NASA's Solar Dynamics Observatory launched aboard an Atlas V rocket Feb. 11, 2010 at 10:23 a.m. EST. After a flawless launch and ascent, the spacecraft separated from the rocket's upper stage to begin a five-year mission to study the sun's energy and its influence on space weather.
SDO was declared an operational mission today at the Goddard Space Flight Center. This means we have shown the spacecraft and instruments are ready to collect science data. The science teams are working on making that data available to the scientists and space-weather public.
We have had haikus and sonnets written about the commissioning phase. Now a First Light poem, written by Stuart Atkinson about the prominence eruption on March 30, 2010.
Check out the launch of the EVE calibration rocket launch at http://lasp.colorado.edu/rocket/rocket_movies.html. It shows the countdown and the rocket flying away.
Today, May 3, at 2:12 pm ET/12:12 pm MT the SDO EVE calibration rocket will launch from White Sands Missile Range, NM. Everything is looking good for an on time launch. No real time video is allowed due to security reasons on the Missile Range, but the CCD data and video from the cameras (one pointing forward, one aft) will be posted as soon as possible. Follow the day's progress at:
SDO has 10 CCDs, 8 inside the science instruments and 2 in the star trackers. The science CCDs operate at very low temperatures. The EVE CCDs are 2Kx2K pixels and operate at -100 C. The HMI and AIA CCDs are 4Kx4K and operate at about -70 C. HMI has 2 high-grade visible light CCDs while AIA and EVE treated their CCDs to make them more suitable for detecting extreme ultraviolet light. To cool a CCD we hook it to a radiator panel and keep the Sun off the panel. Thermal radiation leaving the panel is enough to send into space the small amount of heat generated by operating the CCD.
SDO is moving toward becoming an operational science mission. The data will be available from several sites in a variety of formats. SDO scientists and engineers are working to set up those access points, but we won't be ready for regular data releases until mid-May.
Thursday marked the end of image quality jitter testing on SDO. For the past few days the observatory has spun reaction wheels, rotated high-gain antennas, and moved filter wheels. All this to see how each mechanism affected the staring at the Sun. All of the data must now be analyzed and our fine pointing refined to allow us to stare at the Sun.
The principal investigators of the SDO science investigation teams, Philip Scherrer (HMI), Alan Title (AIA), and Tom Woods (EVE) joined Dean Pesnell and Lika Guharthakurta in an SDO First Light press conference yesterday at the Newseum in Washington, DC. The announcement has garnered a lot of press and many examples of those few solar events that saw fit to appear between March 30 and April 8 are now available. Here is an example from March 30, 2010, just after the AIA CCDs were allowed to cool. Such a lovely prominence eruption at 10 o'clock!
Over the weekend SDO completed the HMI roll maneuvers and began preparing for the image quality jitter tests. The next major activity is to isolate the main engine. First, the isolation pyros on the main engine will be fired to isolate the Helium pressurant and main engine from the observatory. After that is the first 2 Nms delta-H thruster maneuver, used to dissipate momentum.
The EVE cruciform maneuver was completed yesterday. Other tests included the high-gain antenna handover with stagger stepping and no-step requests. These tests are required to keep the observatory from moving too much while taking an image with HMI and possibly AIA.
Today SDO ran the EVE Field of View and HMI/AIA Flat Field calibration maneuvers. HMI tested the re-transmission capability of the DDS by asking for re-transmissions of files that were not successfully transferred.
SDO has continued instrument calibration for the past few days. These included an EVE cruciform and guide telescope monthly calibration. During the cruciform scan SDO left inertial mode (an attitude-control mode) and went into sun-acquisition mode. This was traced to a wrong number in a filter that slowly pushed the spacecraft in the wrong direction until an automated response cause SDO to enter sun-acq mode. The number was fixed and the GT calibration was run.
A sonnet to SDO by one of our systems engineers
Eadweard Muybridge is the father of stop action photography. He developed techniques to look at tumbling humans and moving animals. One of his most famous works was to see whether a galloping horse had all four hooves off the ground at the same time. Muybridge set up a series of cameras on the grounds of Stanford University and took 16 photographs that proved the horse gathered all four hooves under its belly at one instant in the gallop stride.
SDO uses similar techniques to make movies of coronal loops, magnetic fields, and prominence eruptions. We also need to ensure we sample the time intervals quickly enough and our pixels are small enough to see what is actually happening on the Sun. Muybridge answered similar questions as he studied animal locomotion.
Muybridge’s photographs are on display through July 18, 2010 at the Corcoran Gallery of Art in Washington DC.
Last evening the EVE cruciform was completed and the high-gain antenna raster resumed. A cruciform scan is a slow scan in a line through the Sun from East to West and another north to South, about 2.5 degrees in each direction. This is used to map out the field of view of the instrument. The high-gain antennas move quite a bit over a year and the raster scans are used to calibrate the pointing of the antennas.
Sunday was a day to reflect on all of the data we have collected so far on the interaction of the instruments and the spacecraft. This week we begin a series of instrument calibration maneuvers and more testing of the high-gain antennas. First up is the EVE cruciform maneuver.
Today the instruments examined how they affect the pointing of SDO. FIlters and shutters inside the instruments have to rotate into new positions before each exposure, so SDO has a lot things spinning around. Each instrument ran their filters wheels and shutters to see how SDO moved. After that they tested the guide telescopes that are part of AIA. The "Science Reference Boresight" is determined by these guide telescopes, so understanding their behavior is crucial to SDO.
SDO spent another day measuring the jitter of the spacecraft, this time how the motion of the two high-gain antennas affected the pointing of the instruments. The instrument teams helped with these tests while continuing to understand their own observing sequences.
Today SDO worked to understand how the reaction wheels that provide our fine pointing control interact with the spacecraft. SDO needs to point at the Sun very accurately while taking an image every 0.75 seconds (which means rotating shutters and filters), rotating the high-gain antennas to keep them pointed toward New Mexico, and rotate the entire observatory once per orbit to keep it pointed at the Sun. Understanding how the reaction wheels work is a essential step toward getting ready to send out the "firehose" of data SDO will generate.
The doors are open and the CCDs are cold, what's next? For the next several weeks SDO scientists and engineers will work to check out and calibrate the instruments and to coordinate the spacecraft and instruments. I may call it "Focus and Center" but it is a busy time for everyone on SDO making sure these complex instruments do what is needed to get our data. In mid-April we plan to show the world how great the instruments are working at a "First Light Media Telecon."
Around 20:00 UT Monday the AIA CCD heaters were turned off allowing the CCD to temperatures drop rapidly from about +40C to -70C and then slowly settle towards their final temperatures. With that drop in temperature, we saw the camera background decrease markedly, and the image quality in all channels improve dramatically.
The engineering images are beautiful, even though taken in an approximate focus position. Tomorrow, we plan to make a series of focus scans to determine an initial optimal focus, and work will start on calibrating the detector amplifier gains, instrument stabilization system response, etc., which will continue to improve image quality.
SInce opening all nine doors, work has continued getting the instruments ready for normal science operations. HMI continues to work on sequences and the image stabilization system. EVE is working on understanding their data. AIA is looking at solar images superimposed on the thermal background of their still-warm CCDs and updated their on-board flight software.
The AIA CCDs are still warm. On Monday the decontamination heaters will be turned off, and the sequencer will be started so the CCD cool-down can be observed.
All nine SDO instrument doors are now open.