SDO Day 78: Just the CCD Facts, Ma'am

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.

An example of how the Sun affects our satellite fleet happened on April 5, 2010. Unusually violent solar activity caused the Galaxy 15 satellite to stop responding to ground commands. A backup satellite is being moved into position and it is hoped that Galaxy 15 will be recovered.

SDO Day 76: Getting Ready for Science Data

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.

Next step is the EVE calibration rocket, scheduled to fly on May 3, 2010 from the White Sands Missile Range.

SDO Day 73: The End of Jitter Testing

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.

This week also saw the isolation of the main engine. We no longer need the large thrust provided by the main engine and the pipes carrying fuel and oxidizer to it have been closed and sealed. Thanks for the lift!

SDO Day 72: First Light Data is Released

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!

Congratulations to the SDO team members around the world for getting us to the beginning of the science mission.

SDO Day 69: A Weekend Summary

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.

SDO Day 65: Calibration Maneuvers

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.

Next Tuesday we plan to have an Delta-H thruster burn. These momentum unloads are required to keep the reaction wheels spinning at the correct speeds.

Next Wednesday we are having a First Light Press Conference at the Newseum in Washington, DC. Stay tuned for proof that the instruments on SDO are working great!

SDO Day 63.14159: More Tests

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 Day 62: Still Testing After All These Weeks

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.

The EVE cruciform and HMI flat field maneuvers will run Wednesday.

This is why we test!

SDO Day 61: A Shakespearean Paean to SDO

A sonnet to SDO by one of our systems engineers

When sitting down to describe the events of the day,
I realize I’m growing weary of Haiku.
But still I’d like to express myself in some old fashioned way
And at the same time, try something new.
So tonight, I write in the form of a sonnet
Like the Bard would have, centuries ago.
But when it comes to news, though you might want it
I have very little to report that you don’t already know.
The Observatory continues her graceful figure eight,
SDOGS2 remains watchful and ready for command,
But there are no activities planned for this date,
And thus, the uplink is short on demand.
Thus concludes a nominal shift report:
I have expressed myself, and await your retort.

Helios: An Exhibit of Eadweard Muybridge Photographs

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.

SDO Day 58: Rolls are Complete

Our initial Science Reference Boresight was defined Friday. This is the target for the fine-guidance system in science mode, or it is the imaginary line that leaves SDO and hits the center of the Sun. All of the instruments can then figure out where they are pointed with very high accuracy.

SDO completed several calibration maneuvers this week, with more coming in next 10 days. Last nite the HMI/AIA roll was done. While SDO spins slowly around the axis pointing toward the Sun the instruments take measurements at different clock angles to check out their optics. We also tried stepping the high-gain antennas separately rather than together to see if the jitter was different.

The misbehaving high-powered amplifier on the SDO2 antenna was replaced and SDO2 is being brought back into full service.

We have left the vernal equinox eclipse season and look forward to almost 5 months of uninterrupted solar measurements!

SDO EVE Rocket arrives at White Sands

PI Tom Woods and crew arrived in White Sands Missile Range, NM to integrate the EVE calibration rocket on Monday and perform initial checkouts of the payload to make sure it survived. All is going well, and the launch has been moved up to May 3. Upcoming tasks next week are the environmental tests - vibe, spin balance, and bend test. Hopefully we can get ITAR and security approval for pictures quickly and post those here in the near future.

Keep up to date with the status at:

http://lasp.colorado.edu/rocket/rocket_future.html

SDO Day 55: Cruciforms and Raster Scans

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.

Data continues to flow, SDO is GO!

SDO Day 54: A Day of Reflection

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.

SDO is looking good!

SDO Day 52: Instrument Jitter and Guide Telescopes

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 Day 51: High-gain Antennas and Jitter

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.

SDO Day 50: The Wheels on the Spacecraft Bus Go Round and Round

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.