June 30 - Dawn Completes Prime Mission and Continues Observing Ceres
Today marks the official conclusion of Dawn's prime mission, which began when the spacecraft left Earth on September 27, 2007. The mission has far surpassed all of its objectives for exploring protoplanet Vesta and dwarf planet Ceres. Some interesting statistics and other information on the prime mission are here.
Dawn transmitted a large volume of scientific data to Earth on June 27-28, and it is continuing to observe Ceres even as the prime mission concludes. On July 1-2, it will transmit more pictures and spectra from its final mapping orbit at an altitude of 240 miles (385 kilometers).
June 24 - Dawn Making More Ceres Measurements
The spacecraft transmitted a large volume of Ceres measurements on June 22-23 and now is collecting even more stereo photos and spectra of the dwarf planet.
Dawn and Ceres orbit the sun together, independently of Earth. Shortly before 4:00 AM PDT today, the spacecraft was pi astronomical units from Earth, or about 292 million miles (470 million kilometers). One astronomical unit is the average distance between Earth and the sun.
June 17 - Dawn To Complete Orbit Adjustment
Dawn has had another very productive week of operations, but it has still more to do. Occasionally Dawn executes small maneuvers with its ion engine to keep the orbit synchronized with the observation plans. These orbit maintenance maneuvers (OMMs) are always performed in two windows separated by eight or nine days. The first part of the latest OMM was on June 9. Today the spacecraft will complete the OMM, this time with two thrust segments. Starting about 4:00 PM, it will use its ion engine for a little over an hour, and then it will thrust once more for 44 minutes starting shortly after 1:00 AM tomorrow. The combined effect of all three thrust segments is to change Dawn's velocity by about 0.8 mph (1.3 kilometers per hour).
Following the OMM, the spacecraft will point its main antenna at Earth to transmit more pictures and spectra. On June 19, it will resume observing Ceres.
June 14 - Dawn Stereo Mapping Proceeding Well
Yesterday and today the spacecraft transmitted its latest Ceres data to Earth. Now it is taking more stereo photos to reveal the three dimensional character of the alien landscapes. It is also continuing to acquire neutron, gamma ray, visible and infrared spectra of Ceres.
June 9 - Dawn to Adjust Orbit
Dawn started beaming more photographs and spectra to JPL yesterday, and it is continuing today.
Every three weeks, the flight team evaluates Dawn's orbit to determine whether an adjustment is needed. These "orbit maintenance maneuvers" (OMMs) were described in the February Dawn Journal. Most of the OMMs have not been necessary and so were canceled. Now a small refinement is needed, and the first part will be executed this afternoon starting shortly after 4:00 PM. Dawn will thrust with its ion engine for about an hour. The spacecraft will perform more small maneuvers on June 17 and 18.
June 6 - Dawn Operations Remain Smooth
After sending its most recent findings to Earth on June 4-5, Dawn is observing Ceres again, acquiring new photographs and spectra. The mission has already surpassed all of its original objectives for exploring the dwarf planet, and it is continuing to collect bonus data.
May 31 - Dawn Continuing to Study Ceres
Dawn is transmitting its latest pictures and spectra of Ceres to NASA's Deep Space Network.The spacecraft is healthy and all systems are working well. Early tomorrow morning it will resume observing the dwarf planet.
The May Dawn Journal explains how scientists use Dawn's photographs of craters to measure the age of geological features. It also presents some surprising information about samples on Earth from Vesta, which Dawn explored in 2011-2012.
May 26 - Dawn Completes Another Mapping Campaign
Dawn has completed the photography of the Ceres landscapes it began on April 11, pointing its camera slightly ahead and to the left. Combining pictures from that perspective with the earlier pictures looking straight down makes stereo views.
The spacecraft is now transmitting its last set of pictures and other data to Earth. After it finishes tomorrow, it will begin a new photography campaign, this time taking pictures with the camera looking slightly ahead and to the right. These pictures will form new stereo views, allowing further refinements in topographical maps of the alien terrain.
Since arriving in orbit on March 6, 2015, Dawn has now completed more than 1,000 revolutions around the dwarf planet.
May 19 - Dawn Executing All Planned Observations
Dawn is hard at work observing Ceres and storing the data in computer memory. The spacecraft is programmed to pause its measurements early on May 21, when it will turn to point its main antenna to Earth and radio the data to JPL.
Dawn is continuing to operate in "hybrid control," using its two operable reaction wheels in combination with hydrazine to control its orientation. Mission controllers activated the two reaction wheels in December when the probe reached this low altitude orbit. As long as they operate, the two wheels allow the dwindling supply of hydrazine to be used very efficiently.
May 16 - Dawn Operating Smoothly
Dawn is devoting most of today and tomorrow to sending more Ceres data to Earth.
Every three weeks, the flight team evaluates Dawn's orbit to determine whether a small adjustment maneuver with the ion engine is needed. (These "orbit maintenance maneuvers" were described in the February Dawn Journal.) Today the team concluded that the orbit is so good that no maneuver is necessary.
May 13 - Another Lucky Day for Dawn
On this Friday the 13th, Dawn is maintaining its long streak of good luck (supplemented with some skill) in exploring Ceres. The spacecraft began transmitting its most recent pictures and spectra to Earth yesterday and will finish late this morning. It will resume observing the dwarf planet around noon.
May 9 - Dawn's Fourth Mapping Orbit Continues
After beaming its latest Ceres measurements to NASA's Deep Space Network on May 7-8, Dawn is now making still more.
One year ago today, Dawn completed its first mapping orbit around Ceres at an altitude of 8,400 miles (13,600 kilometers) and began spiraling lower. A single revolution at that altitude required 15 days. Now in its fourth mapping orbit, Dawn's altitude is 240 miles (385 kilometers), and its pictures are 35 times sharper. Held tighter in Ceres' gravitational grip, Dawn travels four times faster at this lower altitude, and a single orbital loop now takes less than 5.5 hours.
May 6 - Dawn Performing Well
Dawn is completing another productive week of Ceres observations, taking pictures for topography and collecting spectra for the atomic and mineralogical composition. It will send more data to Earth on May 7-8. While pointing its camera and spectrometers at Earth, the spacecraft broadcasts a radio signal through an auxiliary antenna. That signal is used for precise tracking of Dawn's orbital motion to map the variations in Ceres' gravitational field, which provides insight into the interior structure of the dwarf planet. (All these methods of learning about Ceres have been described in recent Dawn Journals.)
May 3 - Dawn Passes Milestones at Ceres
Dawn is healthy as it continues its mission at Ceres. The spacecraft is transmitting its latest data to Earth today and tomorrow.
Dawn's orbital residence at Ceres now exceeds its time in orbit around Vesta in 2011-2012. And today Dawn's interplanetary journey has been in progress for pi thousand days. For details on these and other milestones, see the April Dawn Journal.
Five years ago today, Dawn began its approach phase to Vesta, including its first photographs of the protoplanet.
April 29 - Dawn Continues Overachieving
Dawn's exploration of Ceres is proceeding flawlessly. The spacecraft has acquired more pictures for mapping Ceres' topography as well as new infrared and nuclear spectra. It sent this large volume of data to Earth on April 28-29 and is now observing Ceres again.
The April Dawn Journal summarizes how many more measurements Dawn has accomplished at Ceres than originally planned.
April 22 - Dawn Mapping Ceres' Topography
Dawn is continuing to take pictures with its camera pointed ahead and to the left as it orbits Ceres, providing stereo views of the dwarf planet's terrain. The spacecraft will transmit its latest pictures and spectra to the Deep Space Network on April 23-24.
The operations team conducted its regular assessment of Dawn's orbit this week. They concluded the orbit was so good that an orbit maintenance maneuver was not needed.
April 18 - Dawn Gathering More Ceres Data
Dawn remains healthy in its lowest orbit around Ceres, 240 miles (385 kilometers) above the alien surface. It is taking new pictures and gathering other data as it circles Ceres every 5.4 hours. Tomorrow morning the spacecraft will begin sending all these measurements to Earth, and the next day it will start collecting even more data.
April 15 - Mapping Progressing Well
After filling its memory with more observations of Ceres, Dawn began transmitting its results to Earth yesterday afternoon. Tonight it will resume studying the dwarf planet.
April 11 - Dawn Beginning New Ceres Mapping
Dawn is taking pictures and collecting spectra of Ceres. It is now pointing its camera and other instruments slightly ahead and to the left as it circles the dwarf planet. With pictures taken at an angle, scientists will have stereo views so they can construct a more detailed topographical map than they developed in the third mapping orbit. (The March Dawn Journal and the links there explain the stereo imaging in more detail.)
On April 9-10, Dawn maneuvered with its ion engine to synchronize its orbit with the plan for observing Ceres. (These orbit maintenance maneuvers are described in the February Dawn Journal.) Then on April 10-11, it pointed its main antenna to Earth to radio its latest observations to the planet where its journey began.
Dawn's main computer is using software controllers installed five years ago this week, shortly before the spacecraft arrived at Vesta. And exactly two years earlier, they also loaded new software. (Follow the link to find out how you can get a copy of the software for your own use, or simply put your computer or smartphone in the main asteroid belt, send us the coordinates, and we'll install it for you.)
April 8 - Dawn to Execute Small Maneuver This Weekend
Dawn is continuing to observe Ceres. Tomorrow it will begin the second half of the orbit maintenance maneuver it performed on April 1 and 2. It will thrust with ion engine #2 for almost two hours starting about 3:30 PM and then again for almost 2.5 hours beginning shortly before 11:00 PM.
After it completes the maneuvering on April 10, the spacecraft will use its main antenna to establish contact with the Deep Space Network and transmit all the data it collected since the last communications session on April 6.
April 5 - Dawn Healthy and Operating Well
Since thrusting with its ion engine on April 1 and 2 to refine its orbit around Ceres, Dawn has been collecting more data on the dwarf planet. It is taking pictures, measuring the gravity field, and collecting infrared, gamma ray and neutron spectra. Shortly after 9:30 AM PDT today, the spacecraft will turn its sensors away from Ceres to point its 5-foot (1.5-meter) antenna to Earth. It will resume its scientific observations by 1:30 PM tomorrow.
April 1 - Dawn to Adjust Orbit
At the end of another productive week, Dawn is transmitting its most recent scientific data to the Deep Space Network . The March Dawn Journal presents some of the mission's latest findings about Ceres.
The spacecraft will start executing an orbit maintenance maneuver (OMM) shortly after 5:00 PM PDT today. It will thrust with its ion engine for a little more than two hours, and then about 1:00 AM PDT on April 2 will begin thrusting again for the same duration. Following that, Dawn will resume its observations of Ceres. The second half of the OMM will consist of two more thrust segments on April 9-10. (OMMs are explained in more detail in the February Dawn Journal.)
March 29 - Operations Team Verifying Dawn's OrbitAs Dawn continues its exploration of Ceres, the operations team is conducting its regular evaluation of the spacecraft's orbit around the dwarf planet. The probe has been doing an excellent job collecting data, but small deviations from the planned orbit gradually accumulate. Occasionally the ion engine is used to perform an "orbit maintenance maneuver," as explained in the (February Dawn Journal.)The team will decide this week whether to adjust the orbit.
Today is the 209th anniversary of the discovery of Vesta. When Heinrich Wilhelm Matthäus Olbers first spotted it, he could hardly have imagined that a ship from Earth would travel to that mysterious point of light among the stars. And yet Dawn did, and it provided a detailed and richly rewarding exploration of the world that Olbers found.
March 25 - Dawn Making New Observations
Dawn is operating flawlessly as it acquires more photos and spectra of Ceres. The explorer transmitted its findings to Earth on March 23-24, and it will send the data it is collecting now on March 27-28.
March 22 - Dawn Revealing New Sights
Dawn is healthy and continuing its observations of Ceres. After transmitting data to Earth on March 18 and 19, the spacecraft began a new set of measurements. Now, instead of looking straight down, it is pointing its sensors a little bit to the left as it circles Ceres. This provides a slightly different perspective on the alien landscape and may reduce the rate at which the probe consumes its dwindling hydrazine propellant. (Hydrazine is essential for Dawn's operation.)
A new view of the famous bright area in Occator crater, photographed by Dawn from the closest it will ever come to the intriguing geological feature, is now available here.You can see other new Ceres images based on Dawn's measurements at the Ceres image gallery.
March 18 - Dawn Concluding Another Week of Observations
After spending most of the week observing Ceres, Dawn paused this morning to point its main antenna at Earth. It is now radioing its precious data to the Deep Space Network. It will resume its measurements tomorrow around noon.
March 15 -Dawn Maintaining Its Productive Exploration Routine
With its suite of sensors pointed at the alien landforms 240 miles (385 kilometers) beneath it, Dawn is collecting more data as it orbits Ceres. It sent its latest findings to Earth on March 13 and 14.
March 11 -Dawn Continuing to Observe Ceres
Dawn is healthy and all systems are operating well as it takes more pictures and acquires more neutron, gamma ray and infrared spectra of Ceres.
On March 13, it will pause its observations to transmit the most recent data to Earth.
Dawn arrived in orbit on March 6, 2015, a historic culmination of an extraordinary interplanetary journey. The explorer began extensive photography of Ceres and measurements of infrared and visible spectra even before Ceres' gravity took hold. The spacecraft's gamma ray and neutron detector was activated on March 12, 2015, even though scientists understood that its detailed measurements would not begin until reaching this low altitude.
March 9 -Orbit Maintenance Maneuvers Deemed Unnecessary
Dawn is aiming its main antenna at Earth, transmitting its latest photos and other measurements of Ceres. It will resume collecting data this afternoon.
As the flight team was working on the details of the orbit maintenance maneuvers described in the March 7 status report, they determined that the current orbital parameters are satisfactory. Therefore, rather than take the spacecraft's time away from observing Ceres to perform the maneuvers to achieve a small improvement in the orbit, they have decided to let it continue to point its sensors at the dwarf planet without these interruptions.
March 7 -Dawn to Adjust Its Orbit
Dawn's exploration of Ceres is continuing to go extremely well. As explained in the February Dawn Journal, the flight team occasionally needs to adjust the spacecraft's orbit to keep it synchronized with the intricate plans for observing the dwarf planet. They have now determined that Dawn should perform a set of "orbit maintenance maneuvers" for this purpose. Mission controllers are now working on the details to send to the spacecraft, and it will use its famously efficient ion engine to thrust for almost 1.5 hours on March 9, then wait for 6.5 hours and then thrust again for shortly over an hour on March 10. It will perform two additional maneuvers on March 17 of just over an hour and just under an hour, with two hours between them.
March 4 -Dawn at Maximum Distance from Earth
As Dawn continues exploring Ceres, today it is at its greatest distance from Earth for the entirety of its extraordinary extraterrestrial expedition. It is more than 3.95 AU (367 million miles, or 591 million kilometers) from its original planetary home. Details and a diagram are in the February Dawn Journal.
Dawn will spend much of today and tomorrow radioing data to mission controllers. It will take the signals almost 33 minutes to travel from the spacecraft to Earth. The probe will resume its scientific observations early tomorrow afternoon.
February 29 -Dawn Surpasses Its Objectives
Dawn is transmitting its latest pictures and spectra to NASA's Deep Space Network today. Shortly before midnight tonight, the spacecraft will turn to point its sensors at Ceres again and resume its observations.
Dawn's long interplanetary adventure to explore two of the last uncharted worlds in the inner solar system has been extremely productive. The probe has successfully completed all of the measurements it was designed to make, fulfilling the objectives set for it many years ago. Nevertheless, it will continue to acquire data as it orbits the distant dwarf planet. For details, see the February Dawn Journal.
February 26 -Dawn Send Back More Valuable Observations
Dawn is wrapping up another good week in its final mapping orbit at Ceres. On Feb. 24-25, it returned a wealth of data including photos, nuclear spectra from its gamma ray and neutron detector and infrared spectra from its visible and infrared mapping spectrometer. It is collecting still more data now, which it is scheduled to send to Earth on Feb. 28-29.
February 22, 2016 -Dawn's Exploration Continuing Smoothly
Orbiting Ceres at about 610 mph (980 kilometers per hour), Dawn circled the dwarf planet five times on Feb. 19-20 with its main antenna aimed at Earth, sending pictures and spectra to NASA's Deep Space Network. Following that, it returned to pointing its sensors at the ground beneath it and has been acquiring more data since then.
February 19, 2016 -Dawn Maintaining Productive Pace of Operations
Dawn has been collecting more data on Ceres this week with its camera and spectrometers, and all systems are working well. It will begin transmitting the results to Earth shortly before 1:00 PM PST today. The probe will resume observing Ceres a little after 4:00 PM tomorrow.
February 16, 2016 -Dawn Working Well at its Fourth Planetary Body
After spending much of Feb. 14 and 15 beaming data to Earth, Dawn is back to photographing Ceres and making other measurements.
Tomorrow is the seventh anniversary of Dawn flying past Mars, robbing the Red Planet of some its orbital energy around the sun in order to help fling the spacecraft on its way to more distant and exotic destinations. Dawn achieved a cosmic bull's-eye in gaining that gravitational boost. The equivalent change in the spacraft's speed was 5,800 mph (9,400 kilometers per hour). In exchange Mars slowed down by a rate of one inch (2.5 centimeters) per 180 million years to keep the solar system's energy account balanced. Dawn has been to four planetary bodies, starting on Earth in 2007, sailing past Mars in 2009, orbiting protoplanet Vesta in 2011-2012, and residing since last year at dwarf planet Ceres, its final home.
February 12, 2016 -Dawn Observing Ceres from its Planned Orbit
Dawn transmitted another large volume of Ceres measurements to JPL via the Deep Space Network on Feb. 10 and 11. Now it is back to observing the dwarf planet, collecting more data, which it will send to Earth on Feb. 14 and 15. Also on Feb. 14, controllers will send new instructions for continuing the program of exploration. We love Dawn, but that goes without saying, so no Valentine's sentiments will be included in the interplanetary messages.
Approximately every three weeks, the flight team analyzes the spacecraft's orbit to determine whether to adjust it with the ion engine. (We mentioned this in the mission status reports on Jan. 19 and 21, and the February Dawn Journal will include an explanation.) Based on their latest assessment, Dawn's orbit continues to be so good that no minor corrections are warranted. The present orbital parameters match very well with the plans for new pictures and spectra. This is the second time in a row that "orbit maintenance maneuvers" were deemed unnecessary.
February 8, 2016 -Dawn Continuing to Study Ceres
Aiming its suite of sophisticated sensors at the ground below, Dawn is orbiting closer to Ceres than the International Space Station is to Earth. The explorer is healthy and continuing to perform all of its duties.
February 5, 2016 -Dawn Seeing More and More of Ceres
Dawn is gathering more Ceres data, circling the dwarf planet every 5.4 hours with its combined gamma ray and neutron detector, infrared mapping spectrometer and camera pointed at the landscapes beneath it. Meanwhile, it is transmitting a broad radio signal through one of its auxiliary antennas so we can track its orbital motion to improve measurements of Ceres' gravity field. Shortly after 9:00 PM PST today, the spacecraft will begin sending its results through its main antenna to Earth.
Dawn has photographed about 90% of Ceres from this low altitude orbit. Many people who share our fascination with that distant alien world ask about new pictures of the famous bright area (or famously bright area) at the center of Occator crater, but Dawn has not observed it yet. That is just the way the orbit has worked out. Mission planners did not design the orbit or the schedule of observations and telecommunications to view any specific targets. Rather, as mentioned in the January Dawn Journal, the team designed them so that over the course of six weeks, the probe would see most of the surface. As we will see in the February Dawn Journal, the first few weeks of LAMO don't contribute to this pattern, so the beginning of the six week period was January 10. By simple coincidence, Dawn will not have the opportunity to see Occator until the very end of that period. Therefore, we all wait patiently. After Occator is photographed, the standard process for releasing images will be followed. The need for accuracy and scientific review of the data sometimes slows the release of some products, but all of the data are released to the public after the science team has performed the necessary analysis and interpretation for scientific publication. It will be worth the wait!
February 1, 2016 -Dawn Mapping Proceeds Flawlessly
Dawn continues to operate flawlessly in its final mapping orbit around Ceres. The spacecraft is pointing its main antenna at Earth today, transmitting its latest pictures and other data. It will resume its observations tomorrow shortly before 10:00 AM PST.
January 25, 2016 -Dawn's High Resolution Observations Continue
After concluding its telecommunications session on Jan. 23, Dawn brought Ceres back into its sights. It has been collecting more data since then as it circles the dwarf planet at an average altitude of 240 miles (385 kilometers).
One year ago today, the spacecraft was 147,000 miles (237,000 kilometers) from Ceres, using its ion engine to approach the alien world. Later in the day, it took its second set of pictures to navigate to the uncharted destination. Those were its photos to surpass the resolution provided by the Hubble Space Telescope. Now Dawn's sharp pictures show about 830 times the detail that Hubble's images revealed. The Jan. 29, 2015, Dawn Journal described the navigation pictures and even looked ahead to the improvement we would achieve in the current low altitude orbit. The last year has been a fantastic period of discovery.
January 21, 2016 -Dawn Collecting Data with Good Orbital Accuracy
Dawn remains healthy and productive, taking photos and spectra of Ceres. It will continue doing so until Jan. 22, when it is scheduled to transmit more of its precious data to Earth.
The spacecraft's orbit around the dwarf planet is close enough to what mission planners had specified for this period that it is not necessary to perform the pair of orbit maintenance maneuvers described in the Jan. 19 mission status update. Instead, the spacecraft will continue pointing its sensors at Ceres during the windows that were scheduled for the maneuvers. The next decision on whether to perform orbit maintenance maneuvers will be in three weeks.
January 19, 2016 -Dawn About to Resume Observing Ceres
The spacecraft spent the weekend filling its computer memory with more Ceres data, and it has been sending those findings to NASA's Deep Space Network since yesterday morning. Shortly after noon PST today, it will resume its observations.
Meanwhile, the flight team is using the latest navigational measurements to determine Dawn's orbit very accurately and calculate what it will be for the next few weeks. Based on these and other analyses, the mission director will decide tomorrow whether Dawn should perform an orbit maintenance maneuver. If so, mission planners already have windows in Dawn's intricate schedule on Jan. 23-24 and Jan. 31-Feb. 1. (Orbit maintenance maneuvers in this low altitude orbit are always done in pairs separated by about eight days.)
January 15, 2016 -Dawn Maintaining its Productive Pace
Dawn used its main antenna for about 26 hours on Jan. 13 and 14 to transmit a wealth of data to Earth. Now the spacecraft is taking more photographs and other scientific measurements while orbiting about 240 miles (385 kilometers) above Ceres’ surface.
Dawn is healthy and continuing to operate smoothly. The two reaction wheels that were activated on Dec. 14 have been functioning well, and the consumption of hydrazine propellant (used in combination with the reaction wheels to control the probe's orientation) is very good.
January 11, 2016 -Dawn Hard at Work Observing Ceres
After completing its orbit maintenance maneuver on Jan. 8, Dawn spent much of the weekend with its main antenna aimed at Earth as it revolved around Ceres, beaming its latest data to NASA's Deep Space Network. Then around 9:00 AM PST on Jan. 10, the spacecraft turned to point its science instruments at the ground beneath it and resumed its program of observations of the dwarf planet. It will continue until 7:00 PM PST on Jan. 13, when it is scheduled once again to start transmitting the precious measurements stored in its memory.
January 8, 2016 -Dawn to Perform Small Orbit Maintenance Maneuvers
After devoting much of the week to observing Ceres, Dawn will execute a pair of burns with its ion engine today to modify its orbit. Starting a little after 1:00 PM, the ship will thrust for less than two hours, wait about six hours as it continues to revolve around Ceres and then thrust again for less than two hours, finishing around 11:00 PM. With its uniquely efficient and gentle ion engine, these small orbit maintenance maneuvers will keep the explorers' orbital motion aligned with the plan the flight team has devised for systematically studying the alien world from this low orbital altitude of 240 miles (385 kilometers). Dawn will spend most of the weekend sending its pictures and other data to Earth. When it has finished on the morning of Jan. 10, it will begin collecting still more data.
January 4, 2016 -Dawn Concludes a Productive New Year's Weekend
After using its ion engine for almost 11 hours on Dec. 31 - Jan. 1 to adjust its orbit slightly, keeping it synchronized with the plan for mapping Ceres, the spacecraft resumed its observations. Since then, it has been taking more pictures and measuring spectra of infrared light and two kinds of nuclear radiation. It has also been sending a radio signal that engineers and scientists use to track its orbit in order to map the interior structure of the dwarf planet. (The radiation and orbit measurements are explained in the most recent Dawn Journal.)
This afternoon the spacecraft will turn to point its main antenna to Earth and then spend about a day transmitting its latest results. Tomorrow afternoon it will turn once again to aim its sensors at the rocky, icy ground and collect more data until its next pause on Jan. 8
December 31, 2015 -Dawn Busy as Year Ends
Dawn is transmitting its latest Ceres observations, orbiting the dwarf planet while pointing its main antenna to Earth. This afternoon the spacecraft will use its ion engine to perform an orbit maintenance maneuver, which will keep its orbit matched with the plan for obtaining good coverage of the world beneath it. Following that, the probe will turn again to point its instruments at Ceres and resume collecting data.
The December Dawn Journal describes the highest priority scientific observations Dawn is conducting in this fourth and final mapping orbit.
December 29, 2015 -Flight Team Preparing Small Adjustment to Orbit
Dawn remains in good health as it continues to take pictures and make other measurements of Ceres. As at Vesta, occasional small adjustments to its orbital motion will be required at this low altitude to keep it synchronized with the observing plan. The flight team is working on the detailed flight plan for the first of these "orbit maintenance maneuvers," scheduled for Dec. 31.
December 23, 2015 -Dawn Observing Ceres Again
Dawn sent its latest measurements to mission control at JPL as it completed five revolutions around Ceres, each lasting about 5.4 hours. Around 11:30 p.m. PST on Dec. 22, it once again aimed its scientific instruments at the rocky, icy surface beneath it and began collecting more data.
December 21, 2015 -New Mapping Proceeding Smoothly
Since Dec. 18, Dawn has been taking neutron spectra, infrared spectra, gamma ray spectra, and photographs of Ceres from the lowest altitude orbit. As the spacecraft revolves around the dwarf planet, it points its sensors at the ground but also switches among its auxiliary radio antennas to use whichever is pointed closest to Earth. That allows engineers and scientists to use the radio signal to measure the orbital motion very accurately to map the gravity field.
Tonight Dawn will turn to point its main antenna to Earth for more than 27 hours. Tomorrow night, after transmitting most of its pictures and other data, it will resume observing Ceres.
December 18, 2015 -Dawn Ready for More Observations of Ceres
While Dawn was taking preliminary pictures and infrared spectra on Dec. 16-17, the flight team was putting the finishing touches on commands the probe will use for further observations that start later today. After the trajectory correction maneuver that completed on Dec. 13, navigators measured Dawn's orbital parameters very precisely. Combined with their latest measurements of Ceres' gravity field, they formulated a new prediction of Dawn's orbital motion over the coming weeks. The detailed plans for observing the dwarf planet then were adjusted to account for this latest information.
December 16, 2015 -Dawn Begins Photography and Infrared Spectroscopy
Dawn is now taking pictures and infrared spectra of Ceres from its new average orbital altitude of 240 miles (385 kilometers). In this fourth and final mapping orbit, the pictures will be four times sharper than those from the previous mapping orbit. Nuclear spectroscopy and gravity measurements began last week upon arrival at this low orbit.
The JPL flight team is continuing to incorporate the latest orbital parameters into the plans for the more intensive observations that will start on Dec. 18.
On Dec. 14, mission controllers activated Dawn's two operable reaction wheels to help conserve hydrazine propellant for pointing and turning the spacecraft. The plan to keep the wheels off until now was devised in 2013 following the failure of the other two wheels in 2010 and 2012. Since then, the wheels have been powered on only for a test of the current control scheme (explained in the November 2013 Dawn Journal) and routine maintenance. They are performing well, but engineers understand that the other two gave no indications of any problems until immediately before they faltered. As long as the wheels do function, they will provide a bonus reduction in hydrazine use.
December 14, 2015 -Dawn Preparing for New Observations
Dawn thrust with its ion engine on Dec. 11-13 to fine tune its orbit. When it finished, it pointed its gamma ray and neutron detector (GRaND) at Ceres. GRaND measures the energies and numbers of these two components of nuclear radiation, from which scientists can determine the abundances of some elements on the dwarf planet.
Navigators are making precise measurements of the adjusted orbit to verify that it meets the needs for the intensive observation campaign that will begin on Dec. 18. In the meantime, the spacecraft will collect more radiation measurements as well as conduct some bonus photography and infrared spectroscopy on Dec. 16-17.
Later today mission controllers will power on two of Dawn's reaction wheels. (Two others failed in 2010 and 2012.) Engineers cannot confidently predict how long the two units will operate, but as long as they do, they will reduce the expenditure of hydrazine propellant, extending the spacecraft's lifetime in this final phase of the mission. When either one fails, Dawn will return to using only hydrazine to control its orientation. (The November Dawn Journal explains this in more detail.)
December 11, 2015 -Dawn Ion-Thrusting to Adjust Orbit
Dawn is now using its ion engine to adjust its orbit. This maneuver (explained in the November Dawn Journal.) will synchronize the spacecraft's orbital motion with Ceres' rotation around its axis to fit with the plan for the extensive observations that will begin next week.
Yesterday while the flight team was preparing Dawn's flight plan, the spacecraft tested its backup camera. Controllers occasionally run the camera through a series of tests to verify that it remains in good condition should the primary camera have a problem. (The test of the camera was performed eight years to the day after its first operation in space.) Although the results have not been analyzed in detail yet, all indications are that the backup is in excellent condition.
December 9, 2015 -Dawn at Lowest Orbital Altitude at Ceres
Dawn completed ion-thrusting on schedule on Dec. 7 and continues to be healthy and operating well in its new orbit. Over the last two days, the flight team has determined that the spacecraft did an excellent job in maneuvering to its planned orbit at an average altitude of 240 miles (385 kilometers). To match Dawn's orbital motion with the intricate plan for observing Ceres, the probe will use its ion engine to perform a small adjustment (known as a "trajectory correction maneuver") to the orbit. Long before the spiral descent began, engineers had calculated that such a maneuver was likely and already had a window planned for this purpose on Dec. 11-13. (This was described in the November Dawn Journal.) They are now developing the detailed flight plan for the spacecraft.
December 7, 2015 -Dawn to Stop Ion-Thrusting Today in Low Altitude Orbit
Dawn is scheduled to conclude ion-thrusting for its spiral descent shortly before noon today. At that time, it will be orbiting about 240 miles (385 kilometers) above Ceres, closer than the International Space Station is to Earth. After it turns to point its main antenna to Earth, navigators will begin to measure its orbital parameters very accurately. During the next two days, they will analyze the orbit carefully and decide on Dec. 9 whether to make an adjustment at the end of the week. (It is likely such a trajectory correction maneuver will be needed.) The November Dawn Journal explains this in more details.
December 4, 2015 -Dawn Closing in on Final Mapping Orbit
Dawn has now reduced its orbital altitude to 270 miles (435 kilometers). The probe is continuing to make excellent progress to its fourth and final mapping orbit.
November 30, 2015 -Dawn Continuing to Thrust to Lowest Ceres Orbit
Dawn is now less than 300 miles (480 kilometers) from the alien world of ice and rock. This last major ion-thrusting period of the mission has been going very smoothly, and the spacecraft will reach its targeted altitude of 240 miles (385 kilometers) next week.
This month's Dawn Journal includes an overview of the plans for when Dawn arrives in its lowest altitude orbit around Ceres.
November 25, 2015 -Dawn Making Good Progress to Lower Altitude
During this spiral descent from the third mapping orbit to the final one, Dawn has paused ion thrusting on Thursdays so JPL mission controllers can transmit an updated flight plan. To give the flight team time off for Thanksgiving, the operations schedule has an update today instead of tomorrow. So this afternoon Dawn will stop thrusting and rotate to point its main antenna to Earth.
The tireless explorer will not take the holiday off. It will spend Thanksgiving using its ion propulsion system to reduce its orbital altitude. It will be thankful that on Nov. 26, its average altitude will be 335 miles (537 kilometers), so it will only have to lower its orbit by about 100 miles (160 kilometers) more.
November 23, 2015 -Dawn's Maneuvering Proceeding Well
As Dawn continues to lower its orbit, today its average altitude is about 355 miles (570 kilometers). At this height, each revolution around Ceres takes about 7.5 hours.
November 20, 2015 -Dawn Reaching Ever Closer to Ceres
Dawn's average altitude today is about 395 miles (635 kilometers). The spaceship is orbiting Ceres at 530 mph (855 kilometers per hour).
Once a week during its spiral descent, Dawn stops ion thrusting so it can point its main antenna at Earth. When it did so on Nov. 19, the JPL flight team transmitted the latest flight plan, which incorporated updates using the navigation data collected one week earlier. (See the Nov. 13 status update.)
November 16, 2015 -Spiral Descent Continuing Smoothly
Dawn's ion engine is continuing to push it to lower orbits. Today the spacecraft's average altitude is about 445 miles (715 kilometers).
All of Dawn's ion thrusting throughout its interplanetary journey of more than eight years has now provided the equivalent of 24,500 mph (39,400 kilometers per hour), far more than any spacecraft has achieved with its own propulsion system. Because of the principles of motion for orbital flight, whether around the sun or any other gravitating body, Dawn is not actually traveling this much faster than when it launched. See here for an explanation of this curious phenomenon.
As Earth and Ceres (carrying its sole companion, Dawn) travel on their own independent orbits around the sun, the distance between them is constantly changing. This morning they were pi astronomical units (292.0 million miles, or 469.9 million kilometers) apart. They are separating at almost 52,000 mph (83,000 kilometers per hour).
November 13, 2015 -Dawn Progressing to Lower Altitude
Today Dawn's average altitude is about 490 miles (790 kilometers).
Following its weekly pattern, Dawn stopped ion thrusting yesterday afternoon to aim its main antenna at distant Earth. The flight team at JPL transmitted an updated flight plan for the descent spiral, and Dawn sent a detailed report on its activities and health during the previous week. In addition, accurate tracking of the radio signal as the spacecraft flew around Ceres provided navigators with new data to calculate the orbit. They will incorporate the results into next week's update.
The only probe from Earth ever to take up permanent residence in the main asteroid belt between Mars and Jupiter, Dawn has now been in that part of the solar system for six years.
November 9, 2015 -Dawn Lowering its Orbit
More than three times as far from Earth as the Sun is, Dawn is using its ion propulsion system to maneuver to its final orbit around Ceres. The spacecraft's average altitude above the alien world today is about 550 miles (885 kilometers).
As Dawn descends, the time to complete one revolution gets shorter, both because the velocity increases and because the distance around an orbit decreases. Today it is 11 hours. In the third mapping orbit, each revolution required 19 hours.
November 5, 2015 -Dawn Descending on Course and on Schedule
As Dawn spirals to lower orbits, its average altitude today is about 620 miles (1000 kilometers). Each week, controllers update the complex flight plan for ion thrusting, so Dawn will pause thrusting this afternoon, turn to point its main antenna to Earth to receive its new instructions, and resume thrusting tonight. Tomorrow the spacecraft will reach to below 600 miles (966 kilometers).
November 2, 2015 -Ion Thrusting to Lower Orbit Continues
Dawn has reduced its average altitude today to about 680 miles (1100 kilometers) as it maneuvers to its final orbit. Because lower orbits require higher velocity (to balance the stronger gravitational pull), the spacecraft is now orbiting the dwarf planet at about 450 mph (725 kilometers per hour). (Orbital velocity in the third mapping orbit, which concluded on Oct. 23, was about 400 mph, or 645 kilometers per hour.)
October 30, 2015 -Dawn's Spiral Descent Proceeding Well
Dawn is continuing to use its ion propulsion system for the gradual descent from the third mapping orbit to the fourth and final mapping orbit. Today the spacecraft's average altitude is about 750 miles (1205 kilometers).
The October Dawn Journal summarizes some of the accomplishments in Dawn's extremely productive third mapping orbit, which concluded last week.
October 26, 2015 - Dawn Maneuvering to Lower Orbit
On Oct. 23, when Dawn was orbiting at an altitude of 915 miles (1,470 kilometers), it started more than seven weeks of ion thrusting to lower its orbit to less than 235 miles (380 kilometers). Today the spacecraft's average altitude is 835 miles (1,345 kilometers).
October 23, 2015 - Dawn To Begin Final Spiral Descent
Dawn has finished transmitting its extensive observations of Ceres to Earth.
About 3:30 p.m. PDT today, the spacecraft will fire up ion engine #2 to start maneuvering to its final orbital altitude. It will take more than seven weeks to spiral down from 915 miles (1,470 kilometers) to less than 235 miles (380 kilometers).
The August 2014 Dawn Journal provided an overview of the plans for the explorer's final mapping orbit at Ceres.
October 21, 2015 - Dawn Completes Topographical Mapping
This morning Dawn conducted its final observations from its current orbital altitude of 915 miles (1,470 kilometers). Following the 12th flight over Ceres' sunlit hemisphere in its sixth mapping cycle in this orbit, the spacecraft rotated to aim its main antenna to Earth. It is now beaming its pictures and spectra to NASA's Deep Space Network.
Next week's Dawn Journal will include a summary of this extremely productive third mapping campaign, which began on Aug. 17.
Ion thrusting to spiral down to the fourth and final orbital altitude will begin on Oct. 23.
October 19, 2015 - Final Mapping Cycle Continuing Smoothly
Dawn is flying over the lit hemisphere of Ceres for the 10th time in the final mapping cycle, taking pictures and measuring spectra. After it completes the 12th revolution on Oct. 21, it will turn to point its main antenna to transmit the data to Earth.
October 16, 2015 - Dawn Halfway Through Sixth Mapping Cycle
This morning Dawn completed observations during its sixth transit over the dayside of Ceres in mapping cycle #6. The spacecraft is continuing to operate extremely well.
The flight team is now developing the detailed flight profile and the associated instructions the probe will follow for its spiral descent from this third mapping orbit to the fourth and final orbit, which it will reach in December. Ion thrusting is scheduled to begin on Oct. 23.
October 12, 2015 - Final Mapping Cycle Underway
Dawn transmitted the last of its measurements from mapping cycle #5 yesterday and started its sixth mapping cycle today at 1:40 a.m. PDT. Mapping cycle #6 will consist of 12 flights over the sunlit terrain, during which the explorer will aim its sensors at the scenery farther behind than in the third mapping cycle but not as far to the right. The pictures will add to scientists' determination of the topography of this alien world. This will be the last set of observations made at the current altitude of 915 miles (1,470 kilometers).
October 9, 2015 - Fifth Mapping Cycle Wrapping Up
Dawn will start its 12th and final passage in mapping cycle #5 over the dayside of Ceres this afternoon. After completing these observations at 1:31 a.m. PDT tomorrow, the spacecraft will aim its main antenna to Earth. It will take about two days to radio all of its photos and other data to NASA's Deep Space Network. Dawn will orbit Ceres 2.5 times while it is transmitting its findings.
The final mapping cycle in this phase of the mission will begin on Oct. 12.
October 5, 2015 - Fifth Mapping Cycle Half Complete
Dawn conducted its sixth observing session in mapping cycle #5 today, spending more than nine hours photographing Ceres and collecting more spectra.
Since entering orbit in March, Dawn has completed more than 100 revolutions around the dwarf planet, with 62 of those occurring since the start of this third mapping phase on Aug. 17.
October 1, 2015 - Dawn Begins Fifth Mapping Cycle
After sending the last of its data from the fourth mapping cycle to Earth, Dawn started its fifth mapping cycle on Sep. 30 at 11:40 p.m. PDT. During this 11-day period, the tireless explorer will aim its sensors toward the terrain immediately ahead as it orbits the alien world at an altitude of 915 miles (1,470 kilometers). This new angle will provide scientists with another stereo view to use in developing 3-D perspectives.
This morning Dawn completed the first transit in this cycle over the side of Ceres facing the sun. The dwarf planet turns on its axis in nine hours, and the spacecraft revolves around it in 19 hours, spending half that time over the sunlit landscape and half over the ground hidden in the dark of night. With 12 orbital loops, Dawn's camera can see all of the terrain.
September 28, 2015 - Fourth Mapping Cycle Nearly Complete
This afternoon Dawn will begin the 12th and final observation session in its fourth mapping cycle. Upon completing this last flight over the illuminated hemisphere, the spacecraft will point its main antenna at Earth for two days to transmit the many pictures and spectra it has acquired.
On Sep. 27, Dawn celebrated its eighth anniversary of being in space. This month's Dawn Journal looks at the spaceship's progress on its interplanetary travels.
September 25, 2015 - Dawn Conducting Fourth Mapping Cycle
Dawn has completed more than half of its fourth mapping cycle, acquiring more stereo pictures as well as spectra in infrared and visible wavelengths. Today the ship will make its eighth transit over the hemisphere of Ceres lit by the sun.
September 21, 2015 - Dawn Conducting Fourth Mapping Cycle
Dawn began its fourth mapping cycle on Sept. 19 at 10:13 p.m. PDT. The probe has now completed two of the 12 revolutions needed to photograph the dwarf planet's entire surface.
For this mapping cycle, the spacecraft points its camera and spectrometers at the scenery ahead and to the left as it orbits at an altitude of 915 miles (1,470 kilometers). Together with the pictures from the other mapping cycles, the different views will allow scientists to develop topographical maps. The visible and infrared mapping spectrometers, which observe a smaller area than the camera, are continuing to study previously unobserved regions with each new mapping cycle.
September 18, 2015 - Observations for Third Mapping Cycle Complete
Dawn completed the observations for the last of its 12 flights over the dayside of Ceres at 12:32 a.m. PDT. It then rotated to point its main antenna to Earth and is now beaming its pictures and infrared and visible spectra to Earth.
The fourth mapping cycle will begin on Sept. 19.
September 14, 2015 - Third Mapping Cycle More Than Half Complete
On Sept. 13, during the seventh transit over the dayside of Ceres in the third mapping cycle, the computer in the camera detected an unexpected condition in the camera and turned off. Engineers observed the situation not long afterwards when Dawn was over the night side of Ceres. In preparation for the next dayside observations, they returned the camera to its normal configuration and confirmed it is healthy.
Today Dawn will observe terrain in the illuminated hemisphere of Ceres for the eighth time. The spacecraft revolves around the dwarf planet every 19 hours, so the twelfth and final dayside pass for this cycle will conclude on Sept. 18.
September 11, 2015 - Dawn Continuing to Map Ceres
Dawn is making good progress on photographing Ceres for its third map. It is also acquiring a wealth of spectra at infrared and visible wavelengths. Today the explorer is making its fourth passage over the lit hemisphere.
September 8, 2015 - Third Mapping Cycle Commences Tonight
Dawn is completing transmission to Earth of the pictures and spectra it acquired during its second mapping cycle while orbiting Ceres at an altitude of 915 miles (1,470 kilometers).
The robotic explorer will begin its third mapping cycle at 12:12 a.m. PDT on Sept. 9. During each of its 12 flights over the dayside of Ceres, it will point its camera and spectrometers behind and to its right, providing a third perspective on the landscape for use in developing topographic maps.
September 4, 2015 - Second Mapping Cycle Going Smoothly
Today Dawn is making its ninth transit over the illuminated hemisphere of Ceres in its second mapping cycle. Throughout this cycle, it is taking pictures and making spectral measurements of the terrain behind and to its left as it orbits the dwarf planet.
The spacecraft will complete its observations for this second map shortly before 1:00 a.m. PDT on Sept. 7. It will then spend almost two days (about 2.5 revolutions around Ceres) transmitting its results to NASA's Deep Space Network.
August 31, 2015 - Dawn's Second Mapping Cycle Underway
Orbiting Ceres at an average altitude of 915 miles (1,470 kilometers), Dawn is photographing the dwarf planet for a new map. Each map requires observations during 12 flights over the dayside of Ceres (plus two more while it transmits the pictures and spectra to Earth). The team calls this one "cycle." (See the August Dawn Journal for more on how the mapping works.)
Today the spacecraft is making its fourth flight over the dayside of Ceres in the second mapping cycle.
August 27, 2015 - Dawn Completes First Mapping Observations
Shortly before midnight last night, Dawn completed its twelfth revolution over the sunlit side of Ceres in this mapping phase. That concluded the observations required to make the first map.
The spacecraft is now pointing its main antenna to Earth and transmitting its precious results. It will continue sending pictures and other data until tomorrow night.
Dawn will begin its second mapping cycle at this altitude around 11:00 PM PDT on August 28. As explained in the Dawn Journal, throughout the second mapping observations, it will point its camera a little back and to the left, rather than straight down, providing provide stereo views from which scientists can construct 3-D views of the alien terrain.
August 24, 2015 - Mapping Proceeding Extremely Well
Today Dawn is making its ninth orbital passage over the illuminated side of Ceres since beginning its new mapping phase. The explorer needs 12 dayside passes (each lasting 9.5 hours, or half an orbit) to see all of Ceres. (This is explained further in the latest Dawn Journal.)
August 21, 2015 - Dawn's New Mapping Phase Off to a Smooth Start
Dawn is performing flawlessly as it takes pictures and collects other data in its new orbit. The spacecraft's view is now three times as sharp as in its previous mapping orbit, which concluded in June.At this orbital altitude, it takes Dawn 11 days to photograph all of Ceres and transmit the data to Earth. The probe is scheduled to map Ceres six times over the next two months. The latest Dawn Journal includes a description of the plans for this phase of the exploration of Ceres.
August 17, 2015 - Third Mapping Campaign to Begin Tonight
The mission control team has now provided Dawn with accurate knowledge of its orbit parameters. They have also completed transmitting all of the other information it needs and confirmed that the explorer is ready for its new Ceres mapping campaign.
Dawn has been pointing its main antenna to Earth since Aug. 13. Shortly after 9:00 pm PDT today it will start rotating to point its camera and other sensors at the landscape below and will begin taking pictures over the north pole less than an hour later.
August 13, 2015 - Dawn Arrives in Third Mapping Orbit
Dawn completed the maneuvering to reach its third mapping orbit and stopped ion-thrusting this afternoon. This was a little ahead of schedule because the spiral descent went so well that some of the allocated thrusting time was not needed. Since July 14, the spacecraft has reduced its orbital altitude from 2,700 miles (4,400 kilometers) to approximately 915 miles (1,470 kilometers). The orbit period has correspondingly decreased from 3.1 days to 19 hours.
Dawn is scheduled to begin its new observations on the evening of Aug. 17 (PDT) and continue for more than two months. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft.
August 10, 2015 - Dawn Resumes Ion-Thrusting After a Day of Planned Coasting
Dawn is now below 1,050 miles (1,690 kilometers) in orbital altitude and using its ion engine to descend further.
Mission controllers formulate the flight plan for the spirals with extra maneuvering time in case it's needed to stay exactly on course. The descent has been going so well that they instructed the spacecraft to coast for almost 23 hours on Aug. 9 and 10. Observations in the next mapping phase cannot begin early for several technical reasons, including the complexity of advancing the carefully timed computer instructions already prepared and the schedule for the Deep Space Network. Therefore, mission planners are keeping the ship close to the originally planned trajectory rather than getting ahead.
August 7, 2015 - Dawn Continuing On Course and On Schedule
Dawn is continuing to use its ion engine to maneuver to a lower orbit. Today it is just above 1,100 miles (1,800 kilometers). It has now reduced its orbital period to about 24 hours. In its targeted mapping orbit at an altitude of 915 miles (1,470 kilometers), the spacecraft will circle Ceres every 19 hours.
August 3, 2015 - Dawn Completes More than Half of Descent
Dawn has completed more than half of the maneuvering to reach its next mapping orbit. The coils in its descent spiral are getting tighter and tighter as it goes. Over the course of the day today, the spacecraft reduces its orbital altitude from 1,300 miles (2,100 kilometers) to 1,250 miles (2,000 kilometers).
July 31, 2015 - Dawn Descent Proceeding Well
Dawn has lowered its altitude to 1,400 miles (2,300 kilometers). Closer to Ceres, where it feels the dwarf planet's stronger gravitational pull, the spacecraft must travel faster in its orbit. It is now circling Ceres at 340 mph (550 kilometers per hour). At this lower altitude and higher speed, Dawn's orbit period is 1.3 days.
Once a week during the descent from the second mapping orbit to the third, the probe pauses ion-thrusting and points its main antenna to Earth. Controllers transmit an updated flight plan during these communications sessions. (This process was explained here.) The communications session yesterday confirmed that Dawn remains healthy and is continuing to perform all of its tasks very well.
The July Dawn Journal includes an updated illustration of the spiral path Dawn is following and presents other details of the adventurer's recent and upcoming activities.
July 27, 2015 - Dawn Orbiting Closer to Ceres
Today the spacecraft is orbiting 1,600 miles (2,600 kilometers) above the ground. As with all of Dawn's complex maneuvers from each mapping orbit to the next, the spacecraft is not taking a perfect spiral path for technical reasons. The altitude does not change as much over the course of the day today as it does some other days. Nevertheless, the probe is accurately following its carefully designed course.
July 23, 2015 - Dawn Maneuvering to Lower Orbit
As Dawn maneuvers closer to Ceres, today it is reducing its altitude from 1,900 miles (3,100 kilometers) to 1,800 miles (2,900 kilometers).
In lower orbits, the spacecraft circles Ceres more quickly, not only because the distance around the orbit is shorter but also because it travels faster in the dwarf planet's tighter gravitational grip. (For more on this, see this Dawn Journal explanation.) In the previous mapping orbit (at 2,700 miles, or 4,400 kilometers), it took slightly more than three days to complete one revolution. Now the orbital period is a little less than two days. When Dawn is in its next mapping orbit (at 900 miles, or less than 1,500 kilometers), each loop will take about 19 hours.
July 22, 2015 - Dawn, Ceres and Earth Closest To Each Other
As Ceres (with its new permanent resident, Dawn) and Earth follow their own independent orbits around the sun, today they are at their closest since June 2014. The dwarf planet and Dawn today are 180 million miles (290 million kilometers) from our home. (For more details and a diagram, see the June Dawn Journal.)
Meanwhile, Dawn is continuing to thrust with its ion propulsion system to shrink its orbit. Today it will descend from 2,000 miles (3,200 kilometers) to 1,900 miles (3,100 kilometers).
July 20, 2015 - Dawn's Spiral Descent Continuing Smoothly
Dawn is continuing to lower its orbital altitude. Today the spacecraft will descend from 2,200 miles (3,500 kilometers) to 2,100 miles (3,400 kilometers).
In its previous mapping orbit, the explorer was 2,700 miles (4,400 kilometers) above the alien world. When it completes its spiral to the third orbit, it will be about 900 miles (less than 1,500 kilometers) high.
July 17, 2015 - Dawn Maneuvering to Third Science Orbit
NASA's Dawn spacecraft is using its ion propulsion system to descend to its third mapping orbit at Ceres, and all systems are operating well. The spiral maneuvering over the next five weeks will take the spacecraft to an altitude of about 900 miles (less than 1,500 kilometers) above the dwarf planet.
The spacecraft experienced a discrepancy in its expected orientation on June 30, triggering a safe mode. Engineers traced this anomaly to the mechanical gimbal system that swivels ion engine #3 to help control the spacecraft's orientation during ion-thrusting. Dawn has three ion engines and uses only one at a time.
Dawn's engineering team switched to ion engine #2, which is mounted on a different gimbal, and conducted tests with it from July 14 to 16. They have confirmed that the spacecraft is ready to continue with the exploration of Ceres.
By the end of the day on July 17, Dawn will have descended to an altitude of about 2,400 miles (3,900 kilometers). After arrival at its next mapping orbit -- called the High-Altitude Mapping Orbit, or HAMO -- in August, Dawn will begin taking images and other data at unprecedented resolution.
July 15, 2015 - Dawn Performing System Checkout in Ceres Orbit
As part of their investigation of the anomaly on June 30, engineers have performed some further configuration changes on the spacecraft, and they are now conducting a test to confirm that all systems are operating well and ready to continue with the exploration of dwarf planet Ceres.
July 13, 2015 - Dawn Healthy as it Orbits Ceres
Dawn remains healthy and functioning normally in its second mapping orbit at Ceres. Engineers are continuing their investigation into the anomaly that caused a discrepancy in the orientation on June 30.
July 6, 2015 - Dawn Holding in Second Mapping Orbit
NASA's Dawn spacecraft is healthy and stable, after experiencing an anomaly in the system that controls its orientation. It is still in its second mapping orbit 2,700 miles (4,400 kilometers) above dwarf planet Ceres.
On June 30, shortly after turning on its ion engine to begin the gradual spiral down to the next mapping orbit, its protective software detected the anomaly. Dawn responded as designed by stopping all activities (including thrusting), reconfiguring its systems to safe mode and transmitting a radio signal to request further instructions. On July 1 and 2, engineers made configuration changes needed to return the spacecraft to its normal operating mode. The spacecraft is out of safe mode, using the main antenna to communicate with Earth.
Dawn will remain at its current orbital altitude until the operations team has completed an analysis of what occurred and has updated the flight plan.
Because of the versatility of Dawn's ion propulsion system and the flexibility of the mission's plan for exploring Ceres, there is no special "window" for starting or completing the spiral to the third mapping orbit. The plans for the third and fourth mapping orbits can be shifted to new dates without significant changes in objectives or productivity.
June 30, 2015 - Dawn Successfully Completes Second Ceres Mapping Orbit
Dawn is over the nightside of Ceres and nearing the end of the eighth and final revolution in its survey orbit phase.
During the observations on June 27, the camera's internal computer reset and about three hours later the computer in the visible and infrared mapping spectrometer reset. The operations team observed both events in telemetry transmitted through one of the spacecraft's auxiliary antennas and concluded no prompt response was necessary. Dawn continued to perform all of its other functions smoothly. (More details are here.)
The second mapping orbit has now concluded successfully. See the June 29 Dawn Journal for a summary of the accomplishments in this mission phase at an altitude of 2,700 miles (4,400 kilometers).
Tonight Dawn will power on its ion propulsion system to begin a spiral descent to the third mapping orbit. It will take about five weeks to complete the maneuvering to an altitude of about 900 miles (less than 1,500 kilometers).
June 25, 2015 - Dawn Performing Penultimate Survey Orbit Observations
Early in the morning on June 24, the spacecraft began its seventh arc over the lit side of Ceres. It has been acquiring spectra and photographs since then. It will cross from the day side to the night side over the south pole later today and will begin transmitting its data shortly after that.
Dawn's final set of observations at this altitude will start on June 27.
June 22, 2015 - Mapping of Ceres Continuing Smoothly
On June 20, Dawn completed transmitting the results of its fifth set of observations. After 10:00 PM PDT that day, it traveled once again 2,700 miles (4,400 kilometers) over the terminator from the night side to the day side of Ceres. The probe is now collecting more pictures and spectra in infrared and visible. After its orbit takes it to the dark side later today, it will turn to point its main antenna to Earth to relay its latest results.
June 18, 2015 - Dawn Now in Second Half of Second Mapping Phase
Dawn is now on its fifth flight over the sunlit side of Ceres in this phase of the mission. It is operating well as it takes more pictures and spectral measurements. The explorer will continue its observations until tomorrow morning when it will pass over the south pole. Then when it flies once again over the unilluminated side, it will send the data to Earth.
During the fourth observing period on June 15, the visible and infrared mapping spectrometer’s internal computer detected an unexpected condition and stopped collecting data. The main spacecraft computer then powered the device off. The same events occurred in 2011 as Dawn was approaching Vesta. This time, as was the case four years ago, engineers and scientists concluded that the most likely cause was a cosmic ray strike. When it was powered back on for the fifth observing cycle, the spectrometer resumed normal operation.
Navigators are continuing to refine their measurements of Ceres’ gravity as they track Dawn’s orbital motion, and they are now using the results to design the next spiral maneuvers with the ion propulsion system. The spacecraft is scheduled to begin lowering its orbital altitude at the end of this month following the conclusion of its eighth revolution.
June 15, 2015 - Dawn Conducting Fourth Set of Survey Observations
On June 13 and 14 Dawn transmitted to distant Earth all of the data from its third dayside observations of Ceres. Yesterday the spacecraft began its fourth trip over the illuminated side of the dwarf planet at this altitude (2,700 miles, or 4,400 kilometers). As Dawn flies south, it will observe the alien world until looping back to the night side again tomorrow morning, when it will start transmitting the results to distant Earth.
June 12, 2015 - Dawn Performing More Ceres Measurements
Dawn is orbiting over the side of Ceres lit by the sun, and it is taking more photos and making other observations. It will travel to the night side again on Saturday and will then turn to point its main antenna to Earth to report its findings.
The veteran explorer remains healthy, and all systems are operating well.
June 10, 2015 - Dawn Completes a Second Round of Observations
Dawn acquired more pictures and other measurements of Ceres in its second arc over the dayside of the dwarf planet. It is now on the night side, sending its precious data to NASA’s Deep Space Network.
Dawn’s third dayside passage over Ceres at this altitude will start tomorrow afternoon and continue for a little more than a day and a half.
June 8, 2015 - Dawn Conducts First Observations in New Science Phase
Dawn photographed Ceres and measured its spectrum in infrared and visible wavelengths as it orbited over the illuminated side on June 5 and 6. All measurements were completed as planned. When its orbit took it to the night side again, the spacecraft pointed its main antenna to Earth and transmitted its findings.
Later this morning it will travel back to the day side and begin its second set of observations.
June 5, 2015 - Dawn Begins New Science Phase
As Dawn flew 2,700 miles (4,400 kilometers) over Ceres’ north pole this morning, the spacecraft passed from the night side to the day side of the dwarf planet. That marked the beginning of the new mapping phase, and Dawn began taking photos and making other measurements on schedule. Circling Ceres every 3.1 days, Dawn will make extensive scientific observations when it is over the sunlit side and will transmit its findings to Earth when it is over the side in darkness. The pictures will be three times as sharp as those from the first mapping orbit. This mapping phase is scheduled to continue for eight revolutions, providing plenty of opportunities to gather a wealth of data.
June 3, 2015 - Dawn Arrives in Second Mapping Orbit
Dawn completed the maneuvering to reach its second mapping orbit and stopped ion-thrusting on schedule this morning. Since May 9, the spacecraft has reduced its orbital altitude from 8,400 miles (13,600 kilometers) to 2,700 miles (4,400 kilometers). The orbit period has correspondingly decreased from 15.2 days to 3.1 days. Dawn is scheduled to begin its new observations on June 5, as explained in the most recent Dawn Journal. First, however, the mission control team will measure the actual orbit parameters accurately and transmit them to the spacecraft.
June 1, 2015 - Dawn Closing in on Second Mapping Orbit
Dawn spent the weekend maneuvering with its ion propulsion system and is now almost in its targeted mapping orbit. Last night it completed its final ascent in this complicated trajectory. Today it is descending from 3,000 miles (4,900 kilometers) to 2,800 miles (4,600 kilometers). It is scheduled to conclude thrusting on June 3 at an altitude of 2,700 miles (4,400 kilometers).
May 28, 2015 - Dawn Receiving Updated Flight Profile
Dawn remains in good health as it has been reshaping its orbit around Ceres. Today the spacecraft orbits from 3,100 miles (5,000 kilometers) up to 3,400 miles (5,500 kilometers) and then will start to descend again. Meanwhile, it paused ion-thrusting this afternoon to point its main antenna to Earth for a routine telecommunications session. Engineers have refined the flight profile based on analyses of the recent optical navigation pictures as well as measurements of the orbit from the radio signal and other data. Controllers are transmitting the new information to Dawn, and it will resume thrusting tomorrow.
Today's Dawn Journal includes a summary of the first mapping orbit, the maneuvering it does between mapping orbits, the second mapping orbit and a suggestion to look at this mission status update.
May 26, 2015 - Dawn Reaching to Lower Altitudes
Dawn is following the carefully plotted trajectory around Ceres, maneuvering to prepare for its second mapping campaign next month. The probe's mapping orbits are nearly circular, but during the flight from one to another, the intermediate orbits are more elliptical. Tonight Dawn's complicated route will take it temporarily below the targeted mapping orbital altitude of 2,700 miles (4,400 kilometers). It will descend to 2,500 miles (4,100 kilometers) tomorrow before beginning another ascent.
On May 22 Dawn photographed Ceres to help the navigation team maintain a tight fix on its orbital position. Controllers used the opportunity to acquire bonus visible and infrared spectra.
May 22, 2015 - Dawn's Orbital Maneuvers Progressing Well
Dawn has made good progress this week continuing to reshape its orbit around Ceres. Today the spacecraft's altitude reaches down to 3,100 miles (5,000 kilometers). Now, as earlier in the week, it will ascend slowly for a while, traveling up to 4,200 miles (6,700 kilometers) on May 24. Even as it climbs, Dawn will continue using its ion engine to maneuver to the next planned mapping orbit at 2,700 miles (4,400 kilometers).
Later today the explorer will stop ion-thrusting to take pictures of Ceres for navigation. This is the second and final photo op between mapping orbits. Dawn will resume thrusting tomorrow.
May 18, 2015 - Dawn’s Complex Maneuvering Continues Smoothly
On May 16, Dawn paused ion-thrusting to observe Ceres for two hours. Navigators use the pictures to help refine the trajectory as the spacecraft winds its way down to lower altitudes. The probe collected bonus infrared and visible spectra as well.
Dawn remains on course for its complex flight from the first mapping orbit to the second. Last week, the spacecraft descended every day. After dipping down to 4,400 miles (7,100 kilometers) on May 17 and 18, now the ship is slowly ascending as it continues to reshape its orbit around the dwarf planet. It will sail up to nearly 5,200 miles (more than 8,300 kilometers) tomorrow before descending again.
May 15, 2015 - Dawn Spiraling Lower
Dawn is using its ion engine to maneuver to its second mapping orbit, which will be 2,700 miles (4,400 kilometers) high. It will reach that altitude in early June.
During the course of the day today, Dawn’s altitude will decrease from 5,500 miles (8,900 kilometers) to 4,800 miles (7,700 kilometers).
Tomorrow the spacecraft will pause ion-thrusting to take pictures of Ceres for navigation.
May 11, 2015 - Dawn Spiraling to Lower Altitude
On May 9 Dawn began the spiral descent to its second mapping orbit. Today the spacecraft is at an altitude of about 8,000 miles (13,000 kilometers).
May 8, 2015 - Dawn Completes First Mapping Campaign
Yesterday Dawn successfully completed its final observations in this mapping orbit, focusing on Ceres' southern hemisphere. It is transmitting the pictures and other scientific data to Earth now.
It takes about 15 days to make one orbital revolution around Ceres at this altitude (8,400 miles, or 13,600 kilometers). Today the spacecraft completed one revolution since its arrival in this orbit on April 23. It is scheduled to start ion-thrusting tomorrow to spiral down to its second mapping orbit. (The orbital spirals were described in the April 2014 Dawn Journal.)
May 6, 2015 - Dawn Observes Ceres' Equatorial Region
The spacecraft is continuing to perform flawlessly in its first mapping orbit at Ceres. Last night Dawn completed its second set of dayside observations at this altitude. Earlier in the evening, the probe flew southward over the equator as it was taking pictures and making other measurements. It is now relaying its findings to Earth.
May 4, 2015 - Dawn Observes Ceres' Northern Hemisphere
Now orbiting over the side of Ceres illuminated by the sun, Dawn collected images and spectra of the northern hemisphere yesterday and today. It is sending its findings back to Earth today and tomorrow.
May 1, 2015 - Dawn Completes Night Side Measurements
Dawn concluded its observations from the night side of Ceres today. It is now transmitting to Earth the large volume of data it collected.
At this altitude, it takes just over 15 days to complete one revolution around Ceres. Dawn's leisurely orbit will bring it from the night side to the day side later today. The spacecraft is scheduled to observe Ceres again on May 3-4 while it flies over the northern hemisphere on the day side. For the complete schedule of observations in this first mapping orbit, see the March 31 Dawn Journal.
April 29, 2015 - Dawn Observing Ceres Again
Dawn is observing Ceres from the night side of the dwarf planet. On April 27 and 28, the spacecraft transmitted to Earth the data it had collected during its first science observations of the southern hemisphere. Its orbit is taking it north, and it passed over the equator on April 28. Although the ground directly beneath it is still in darkness, it is viewing the illuminated terrain of the northern hemisphere, much like a crescent moon.
April 27, 2015 - Update: Dawn Enters Science Orbit
Dawn began its science operations at 7:25 p.m. PDT/10:25 p.m. EDT on Friday, April 24 and performed as expected over the weekend.
April 24, 2015 - Dawn Enters Science Orbit
NASA's Dawn spacecraft entered into its first science orbit on Thursday, April 23, as scheduled. Following a delay in communicating a command sequence, the spacecraft briefly entered into safe mode and awaited further instructions, which were sent by mission controllers. As of early Friday, April 24, the spacecraft returned to normal operating mode and the mission team continues to prepare for science data collection
April 23, 2015 - Dawn Commences its First Science Oribt
Launched on September 27, 2007, the Dawn spacecraft is finally ready to embark on its prime science campaign at Ceres. On April 23rd, at around 1:00 AM PDT, Dawn completed the ion thrusting necessary to shape its first mapping orbit "RC3." Dawn is now in a circular, polar orbit about 8,400 miles (13,600 km) in altitude with an orbit period of about two weeks.
The most recent Ceres pictures show the famous bright spots again (Ceres' Bright Spots Come Back Into View | NASA). These final images of the approach phase were taken from a vantage point 14,000 miles (22,000 kilometers) above the north pole as the spacecraft crossed the terminator from the dark side of the dwarf planet to the lit side.
Dawn maneuvered extensively with the ion propulsion system to reach this mapping orbit. Since entering orbit around Ceres on March 6, it has changed its velocity by 250 mph. The total velocity change accomplished since launch is 24,000 mph (nearly 39,000 kilometers per hour.) This is not the speed Dawn is traveling, however. See the February 2013 Dawn Journal for an explanation of the velocity change.)
March 31, 2015 - Dawn Closing in on Ceres
Dawn is in an elliptical orbit at an altitude of 40,000 miles (64,000 kilometers), traveling at 73 mph (117 kilometers per hour) relative to Ceres. The spacecraft passed the highest point of its elliptical orbit on March 18, where Ceres' gravitational pull was the weakest and Dawn's orbital velocity the lowest, and is closing back in on the dwarf planet, slowly picking up speed.
The spacecraft is still on the shadowed side of Ceres. It is continuing to use its ion propulsion system to reshape its orbit, targeting its first circular science orbit at an altitude of 8,400 miles (13,500 kilometers), which it is on schedule to achieve on April 23. For more information, read this month's Dawn Journal.
February 28, 2015 - Dawn Approaching the Dark Side of Ceres
Dawn is in the final stages of its approach trajectory to Ceres and will slip into orbit around the dwarf planet March 6, 2015. Dawn halted ion thrusting four times this month to take pictures of the dwarf planet for use in navigation. The spacecraft reached its closest distance to Ceres this past week. On Feb. 23 it was less than 39,000 kilometers (10% of the Earth-moon distance); Dawn will not be that close again until early April. This month's Dawn Journal and a new video: Destination Ceres: Breakfast at Dawn, explain Dawn's unique trajectory to Ceres and what we can anticipate when science orbits begin in April.
January 29, 2015 - Dawn Approaching Ceres and Seeing the Sights
Dawn devoted November to ion thrusting, and it is now about three times as far from Ceres as the moon is from Earth. As Earth and Dawn follow their separate orbits around the sun, they are moving to opposite sides of the solar system's star. To learn how to use the sun to locate Dawn early in December, see the November Dawn Journal, which also describes the new route the spacecraft will take into orbit around the dwarf planet.