| Updates
Dawn Conducts a New Solar Array Test and Routine Maintenance
September 30, 2008
Dawn continued to operate smoothly in September. Most of the month was devoted to ion thrusting, including September 27, the first anniversary of launch.
On September 22, operators conducted a revised version of the solar array test executed in July. This new test worked well, and it provided the data required to finalize a technique for calibrating the solar array power.
The spacecraft ended the month in a period of planned coasting that began on September 29. This time is used to perform periodic maintenance routines on some components.
Dawn Reaches Greatest Distance from the Sun for 2008
August 30, 2008
Dawn spent most of August continuing to thrust with its ion propulsion system. On August 8, it reached its greatest distance from the Sun this year of 1.68 times Earth's average distance from the Sun. For the rest of 2008, it will gradually travel closer to the Sun. The spacecraft's elliptical orbit will never bring it as close to the Sun as Earth's orbit. In 2009, it will resume moving away from the Sun.
On August 26, the primary and backup science cameras were commanded to execute standard calibration procedures. The results verify that the cameras remain in good health.
Dawn Conducts a Solar Array Test and Updates Software
July 31, 2008
Dawn completed another month of thrusting, as it passed outside the orbit of Mars. It stopped thrusting for two days this month to perform other activities.
Controllers conducted a test on July 21 of a method to determine how much power the solar arrays could produce (the spacecraft consumes less than the arrays generate while still this close to the Sun). The test did not provide the full set of calibration data that was wanted, but it yielded enough information to guide engineers to minor modifications of the design for the backup calibration opportunity.
On July 22, operators installed an update to software in one of the auxiliary computers to further harden it against the affects of space radiation.
Dawn Switches to Ion Thruster #1 and Continues Thrusting
June 30, 2008
Dawn devoted most of the month to continuing to thrust with its ion propulsion system.
Based on the thermal tests conducted last month, engineers determined that it was safe to switch to ion thruster #1 this month. Therefore, on June 18, when it was time to resume thrusting after pointing its main antenna to Earth, Dawn began using that thruster for the first time since October. Data returned from the spacecraft the next day verified that all temperatures were within their required ranges.
Dawn Conducts Routine Spacecraft Maintenance and Tests for Future Thrusting
May 30, 2008
Dawn devoted most of the month to continuing to thrust with its ion propulsion system.
A planned coast period from May 12 to 14 let the operations team conduct periodic maintenance. Some computer memory locations were checked and verified to be healthy. One of the three powered
reaction wheels was turned off and the fourth wheel was powered on. All gyroscopes were powered on and operated for two days.
To investigate the temperatures that would be experienced for future long-duration thrusting with thruster #1, the spacecraft spent a few hours in the orientations that would be required. The resulting temperature data will contribute to determining when to switch from thruster #3 to #1.
Special Activities Conducted During First Part of April
April 30, 2008
The month began with a non-thrusting period, scheduled to allow special activities.
1. The Gamma Ray and Neutron Detector (GRaND) was operated for about a week to collect data on the "noise" cosmic rays create in its detectors. By making such measurements, scientists will be able to compensate for this noise when GRaND Is operated at Vesta and Ceres.
2. The visible and infrared mapping spectrometer (VIR) observed the star Canopus and Mars. Both are well characterized, so these observations aid in calibrating VIR's detectors.
3. New software was transmitted to both science cameras, and tests confirmed that the software operates correctly.
4. A software patch was loaded into the spacecraft's backup main computer, bringing it to the same version already operating in the primary computer.
5. A test of the pointing accuracy of one of the ion thrusters was interrupted when software detected a signal that appeared incorrect.
The combined attempt to process the response from other software and commands sent by the mission operations team led to a conflict and the computer called "safe mode." After controllers returned the spacecraft to its normal configuration, ion thrusting resumed on April 14.
Meanwhile, engineers established that the software that interrupted the thrust test did so because of an unnecessary step. On April 21 they updated the software, removing that step.
The rest of the month was devoted to ion thrusting, as usual.
Dawn Completes Another Month of Thrusting
March 31, 2008
Dawn thrust with its ion propulsion system for most of March, stopping once each week to point its main antenna to Earth. Almost 96% of the month was devoted to thrusting. By the end of March, the spacecraft was farther from Earth than the Sun.
Thrusting Continues and Backup Framing Camera Tested
February 29, 2008
Dawn continued ion thrusting through most of February. On February 21 and 22, the backup framing camera was put through a series of tests to demonstrate its performance. The camera successfully completed all the steps, and analysis shows the instrument is healthy and operating as expected.
Thrusting Continues and Software Updated in Main Computer
February 1, 2008
Dawn spent most of January continuing with ion propulsion thrusting. A cosmic ray that hit an electronic component on January 15 caused an interruption in thrusting for a few days. Thrusting halted on schedule on January 22 so the operations team could update the software in the main computer. The changes account for the increasing distance from Earth by lowering the speed of communications with Earth when the spacecraft enters "safe mode," the configuration called by software to resolve certain errors. Following the software changes, thrusting resumed on January 25.
Interplanetary Cruise Continues
January 2, 2008
Dawn has continued thrusting with its ion propulsion system since December 17. Following programmed instructions, it interrupted thrusting on December 26 and on January 2 to point its main antenna to Earth to report on its status. All systems are performing well. Now that Dawn is in interplanetary cruise, these updates will occur less frequently.
Interplanetary Cruise Begins
December 17 - 21, 2007
With the successful completion of the initial checkout phase of its mission, Dawn began the interplanetary cruise phase. While other activities will be conducted occasionally, the project's focus now is on thrusting with the ion propulsion system to reach asteroid Vesta (and later dwarf planet, Ceres).
More Instrument Tests Completed
December 10 - 14, 2007
The backup science camera was powered on for the first time this week and verified to be healthy and operating well. The primary science camera and the visible and infrared spectrometer completed additional
tests, and both instruments continue to perform extremely well.
Additional Camera Tests and Software Loads Completed
December 3 - 7, 2007
The primary science camera was operated again, acquiring images of stars as a further test of its performance. All indications are that it is operating excellently. Software that had been uploaded earlier in the mission continues to work well, so the same software was loaded this week into some of the backup locations.
Updated Software Loaded in Main Computer
November 26 - 30, 2007
This week was devoted to updating the software on the main spacecraft computer. This was planned before launch. Files were transmitted to the spacecraft, computer memory was checked, and other activities were conducted on Monday and Tuesday in preparation for rebooting the computer on Wednesday to start using the new software. On Tuesday night, the computer rebooted on its own. All diagnostic information has been returned from the spacecraft and the event is being investigated. With the new software operating as expected, controllers have verified that the spacecraft is healthy and activities are proceeding as scheduled.
Main Antenna Checked Out and New Software Uploaded
November 19 - 23, 2007
This week, the spacecraft was commanded to use its main antenna for the first time and measurements showed that it is in fine condition. New software was installed in one of Dawn's computers (and its backup), correcting a minor bug that was discovered shortly after launch.
More Ion Thrusting Tests Completed
November 12 - 16, 2007
The week-long systems test of interplanetary cruise thrusting completed successfully on Monday. The third ion thruster was tested this week, and like the other two, it performed perfectly. The thruster operated
at 4 throttle levels, including full power. In a separate activity, the mission operations team powered off the reaction wheels to test pointing control with hydrazine thrusters during ion thrusting.
Dawn Begins Cruise Thrust Test
November 5 - 9, 2007
To test the readiness of all systems for the interplanetary cruise phase of the mission (planned to begin in mid-December), Dawn is conducting a one-week execution of all the activities that will be typical of a week in that phase. As most of the time will be spent thrusting with the ion propulsion system, the spacecraft began thrusting on Monday and now has thrust for 4 days without interruption.
More Checkouts Completed
October 29 - November 2, 2007
The operations team conducted tests of special modes of the attitude control system while the ion propulsion system is thrusting. All tests showed excellent performance. Two of the three ion thrusters have been fully checked out. Tests began with the third thruster this week, and all were completed successfully. The device that emits electrons to ionize xenon was heated to drive off contaminants, and then the thruster ionized xenon (but was not commanded to accelerate it). In addition, the gimbal system that points the thruster in the required direction was operated for the first time in flight. The first test of thrusting with this thruster is not scheduled to occur until after other spacecraft tests are completed.
Second Ion Thruster Checkout Completed Successfully
October 22 - 26, 2007
The mission operations team completed the checkout of a second ion thruster this week. In one of the tests, the thruster was operated for 27 hours continuously at 5 different throttle levels, and in two other tests it was operated at maximum power for 4 hours each time. All spacecraft systems performed extremely well.
Science Instruments Checked Out
October 15 - 19, 2007
Dawn's science instruments were powered on and given their first health checks this week. The gamma ray and neutron spectrometer, imaging camera, and visible and infrared mapping spectrometer all operated
perfectly.
Ion Propulsion System Testing Continued
October 8 - 12, 2007
The ion propulsion system performed extremely well as Dawn operated two of its three ion thrusters this week. Testing of the second thruster included placing the spacecraft in an orientation in which sunlight gradually warmed some other components more than mission controllers wanted, and the spacecraft was commanded to end the activity early. The spacecraft remained healthy throughout.
Ion Propulsion System Tested
October 1 - 5, 2007
Mission controllers completed the configuration of the spacecraft for routine operations on September 29. During the week, all the steps were completed to prepare for the first test of ion thrusting.
Dawn Launches!!
September 24 - 28, 2007
Dawn had a beautiful ride to space on September 27. Launch was delayed one day from bad weather, and liftoff was delayed 14 minutes from a boat in the range safety zone. Following liftoff at 7:34 am EDT, all systems performed well, and the operations team at JPL received signals from the spacecraft about two hours later showing that it was healthy. Since then, operators have been checking telemetry and configuring the spacecraft for routine operations.
All Systems Preparing for Launch
September 17 - 21, 2007
Despite two days of delays from bad weather, the payload fairing was installed on the Delta rocket this week, and all systems are on schedule for launch on September 26. The operations team has now
tested and verified all computer files necessary for launch and early operations. All that needs to be completed before launch is fueling and other final preparations of the launch vehicle.
Dawn Spacecraft Returned to Launch Pad
September 10 - 14, 2007
On September 11, Dawn and the mated third stage were moved from Astrotech to Cape Canaveral's Space Launch Complex 17B where they were hoisted into place atop the second stage of the Delta launch
vehicle. Brief tests of the spacecraft subsystems showed Dawn to be in good health. As part of the planned preparations for launch on September 26, the Kevlar cords that have held the solar arrays in their stowed position since prior to the planned June/July launch were replaced with fresh ones, and the new cords were adjusted to the correct tension for launch.
Preparations for Mission Operations Continue
September 3 - 7, 2007
The operations team continued development of command sequences to be used during the first phase of the mission, known as initial checkout. These commands will guide the spacecraft through activities to provide data for engineers to use in evaluating the health and performance of all subsystems. Meanwhile, plans were completed for transporting the spacecraft back to the launch pad next week.
Operations Team Simulates Launch and Operations
August 27 - 31, 2007
The operations team conducted simulations at JPL this week covering the last 16 hours of countdown, launch, and early operations. The simulation supervisor intentionally created some problems, all of
which the team handled successfully.
Launch Period Established
August 20 - 24, 2007
This week, NASA chose September 26 to October 15 as Dawn's launch period. Computer files that will be used during the final countdown were tested on the spacecraft, demonstrating that they work correctly.
Dawn Team Continues Preparing for New Launch Date
August 13 - 17, 2007
The Dawn operations team continued to develop new sets of commands and other computer files for
the spacecraft to use, accounting for differences between the previous launch period and the new
September - October launch.
Launch Coordinates Calculated
August 6 - August 10, 2007
Engineers completed calculations of the coordinates needed for the rocket to deliver Dawn to space for a launch on any day from September 7 through October 15. (The dates for Dawn's launch period will be
established soon.) These data will be used to program the rocket and to compute the open and close times of the daily launch windows. Now, with the details of the new trajectory early in the mission, the operations team is refining commands it will use during the first few weeks of Dawn's flight.
Spacecraft Tests Completed
July 30 - August 3, 2007
Engineers completed a series of tests that verified all subsystems are healthy after transportation from the launch pad back to Astrotech.
Spacecraft Moved to Astrotech
July 23 - 27, 2007
The spacecraft and third stage were removed from the launch pad and transported to a clean room at Astrotech. The first and second stages of the launch vehicle will remain on the pad (until liftoff).
Preparations Continue for Removal of Spacecraft from Launch Pad
July 16 - 20, 2007
The payload fairing (the rocket's nose cone) has been removed. Tests confirmed that the third stage may be moved safely without removing any of its liquid propellant, clearing the way for the spacecraft and mated stage to be transported from the launch pad to Astrotech.
Preparations Underway for September Launch
July 9 - 13, 2007
Work has begun to remove the spacecraft from the launch pad and return it to the clean room at nearby Astrotech Space Operations. (The spacecraft will remain mated to the third stage.) Launch trajectories for September are being designed
Launch Rescheduled for September
July 2 - 6, 2007
Because of consistently bad weather and technical problems with launch vehicle tracking systems off the coast of Africa, Dawn's launch has been rescheduled to September.
Dawn Moved to Launch Pad
June 25 - 29, 2007
The Dawn spacecraft and third stage were transported from Astrotech to Space Launch Complex 17B at Cape Canaveral and installed on the second stage. Final checkouts and preparations for launch continue on all three stages of the launch vehicle and the spacecraft. +
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Spacecraft Mated to Third Stage, and Second Stage Mated to First Stage
June 18 - 22, 2007
The spacecraft was connected to the third stage of the launch vehicle at Astrotech. At Space Launch Complex 17B, the second stage was lifted into place on the first stage.
Hydrazine Loaded, Spin Test Completed, Operations Rehearsals Conclude
June 11 - 15, 2007
Hydrazine propellant, used as one means to rotate the spacecraft in space, was loaded. Spin tests were completed and balance masses were added to the spacecraft. During preparations for the spin tests, minor damage to the back of a solar panel occurred when a tool made inadvertent contact with it. The small affected area was patched over the weekend, and the process did not affect the launch date.
The mission operations team conducted more simulations of activities to be conducted in flight. The entire set of simulations to be executed before launch has now been completed.
New Launch Date Set, Xenon Loaded, Operations Rehearsals Conducted
June 4 - 8, 2007
Because of delays in assembling Dawn's rocket at Cape Canaveral, Dawn's new launch date is July 7. Xenon propellant for the ion propulsion system was loaded into the spacecraft. Meanwhile, the mission operations team conducted additional simulations of launch and early flight activities.
Dawn Spacecraft Prepared for Fueling
May 28 - June 1, 2007
In preparation for loading xenon and hydrazine propellants, the Dawn spacecraft was moved to the fueling area at Astrotech.
Final Operations Test with Spacecraft and Attachment of Solar Arrays
May 21 - 25, 2007
The final mission operations test with the spacecraft was completed successfully. Dawn's solar arrays were attached to the spacecraft and the system for deploying them in space was given one final test, which went very smoothly.
The Dawn project had a large display at JPL's Open House, attended by more than 32,000 people.
Telecommunications Tests Conducted and Observations of Vesta Completed
May 14 - 18, 2007
The spacecraft conducted a successful series of radio communications tests with MIL-71, the facility at the Kennedy Space Center that replicates a Deep Space Network station. The Hubble Space Telescope observed Vesta, the first of Dawn's two destinations.
Spacecraft Alignments Completed and Launch Rehearsal Conducted
May 7 - 11, 2007
The alignment of spacecraft components was verified and finalized this week, ensuring that antennas, ion thrusters, scientific instruments, and other devices are properly oriented. With mission control at JPL connected to the spacecraft at Astrotech in Florida, mission controllers conducted another successful simulation of the final 4 hours of countdown, launch, and the first 4 hours of spacecraft operations once Dawn is in space. (This was a test of the procedures used to control the spacecraft and assess its condition; the launch vehicle was not involved.)
Comprehensive Performance Tests Completed
April 30 - May 4, 2007
The spacecraft successfully completed two weeks of comprehensive performance tests. In these tests, each engineering subsystem and each instrument is operated extensively to verify it continues to function as required. The first run of the same tests was conducted in 2006, so engineers can verify that now that the spacecraft is in final preparation for launch, no unexpected changes have occurred as a result of the environmental tests or the shipment of the spacecraft.
Mission Control Simulation of Ion Thrusting Completed
April 23-27, 2007
Mission controllers completed a four-day simulation of the procedures to be used to command and monitor the spacecraft for the first firing of the ion propulsion system after launch. This activity, known as an operational readiness test, used a simulator of the spacecraft to provide realistic responses to commands as well as signals for engineers in mission control to interpret. This simulation included the steps that would be followed to check the validity of the commands if the launch were delayed by a day, which would cause the alignment of the ion thruster relative to Earth to change. (A launch delay can occur as a result of bad weather or problems during the final countdown that cannot be resolved during the daily launch window.) Meanwhile, the final comprehensive performance tests are being conducted on the spacecraft in Florida to verify that each subsystem is still working correctly.
Work on spacecraft in full swing in Florida
April 16 - 20, 2007
Dawn's solar arrays, which convert sunlight into electricity, arrived at Astrotech Space Operations this week, where work continues on the spacecraft. (The solar arrays were removed from the spacecraft in December.) Version 6.1 of the software for the main spacecraft computer was loaded into the computer. Tests to show that software could be loaded onto the spacecraft while it is in space were completed successfully.
Dawn spacecraft shipped to Florida
April 9 - 13, 2007
The spacecraft was trucked from the Naval Research Laboratory in Washington, DC to Astrotech Space Operations near Cape Canaveral this week. It was unpacked and moved into a clean room, and inspection showed it to be in fine condition after the trip.
Completion of Additional Testing and New Launch Date
April 2 - 6, 2007
An acoustic test, in which powerful sound was directed at the spacecraft (similar to the noise of launch), was completed at the Naval Research Laboratory. This verified that the work to remove and reinstall the high voltage electronics assembly did not harm the spacecraft. To accommodate a change in the schedule for assembling the components of Dawn's Delta II launch vehicle, the launch date is shifted 10 days to June 30. The change will have no effect on mission objectives or science.
High voltage electronics reinstalled and leak checks completed
March 26 - 30, 2007
The high voltage electronics assembly (the unit that governs the delivery of electrical power from the solar arrays to the onboard subsystems) completed testing in a thermal vacuum chamber at JPL and has been reinstalled on the spacecraft at the Naval Research Laboratory. Tests of the ion propulsion system and the reaction control system (the system that uses small conventional thrusters to aid in orienting the spacecraft in the zero-gravity of spaceflight) verified their integrity, with no leaks being found.
Successful completion of tests coordinating flow of information between the Dawn spacecraft and ground systems network
March 5 - 9, 2007
Dawn has successfully completed all of the tests focused on the flow of information between the spacecraft and the network of ground systems that could be conducted before the spacecraft is in Florida. (Testing in Florida will be conducted with a facility near the launch site that replicates the characteristics of NASA's Deep Space Network communications facilities.) The content of version 6.0 of the software that runs in the main spacecraft computers was finalized this week.
GRaND functional testing, reported by Tom Prettyman at LANL
December, 2006
December 16-17, we completed functional testing of GRaND following spacecraft (S/C) vibe and pyroshock. GRaND performed nominally and is ready to proceed to the next phase of environmental testing.
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Solar Array Panels Attached to Dawn Spacecraft
October, 2006
Although the individual components of the spacecraft have already been tested, the point of the testing in Orbital Sciences Corporation's Environmental Test Facility is to verify that the fully assembled spacecraft will survive the rigors of launch and be able to fulfill its ambitious mission of exploration in deep space.
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Dawn Spacecraft in Cleanroom at Orbital Sciences
September, 2006
Technicians complete the interior assembly of the spacecraft before installing the panels.
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Dawn Spacecraft Placed in Thermal Vacuum Chamber
August, 2006
The Dawn spacecraft was moved into a vacuum chamber in the cleanroom and was baked for about a week for the purpose of driving off undesirable contaminants.
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Dawn Mission Reinstated
March 27, 2006
NASA senior management announced a decision Monday
to reinstate the Dawn mission, a robotic exploration of two
major asteroids. "We revisited a number of technical and financial
challenges and the work being done to address them," said NASA
Associate Administrator Rex Geveden, who chaired the review
panel. "Our review determined the project team has made substantive
progress on many of this mission's technical issues, and, in
the end, we have confidence the mission will succeed."
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2006 Mission Status
On March 2, 2006 NASA cancelled the DAWN mission. The Dawn
spacecraft would have visited two of the solar system's largest
asteroids, Ceres and Vesta, during a nine-year voyage .
2005
Mission
Status
Updates
from the
Dawn Project
Manager
Oct.
3, 2005
The second
Framing
Camera
was delivered
to Orbital,
and bench
checkout
completed.
Both Framing
Cameras
are waiting
integration
on the
spacecraft.
The first
Power Processing
Unit (PPU)
for the
ion propulsion
system
is complete,
and has
been delivered
to Orbital.
The second
PPU is
in environmental
testing.
The three
gimbal
assemblies
for the
ion thrusters
have been
delivered
to Orbital,
and the
two outboard
units have
been mechanically
integrated
on the
spacecraft.
Spacecraft
integration
and test
is progressing
very well.
Stay up-to-date with the Dawn mission as we prepare for launch
by visiting our Web site at: http://dawn.jpl.nasa.gov
Framing
Camera Arrives
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