Wednesday, August 17, 2016

Station Keeping Maneuver Today and the Next Lunar Transit

Today from 2240-2305 UTC (6:40-7:05 p.m. ET) SDO will execute a station-keeping maneuver that keeps us within our assigned longitude box. The instruments may return data during this time, but it could be blurry.

Looking forward to September we have another lunar transit on September 1, 2016 from 0715-0731 UTC (3:15-3:31 a.m. ET). This transit will start while SDO is in the shadow of the Earth. That means when we see the Earth move out of the way the Moon will be covering part of the Sun. While these double transits did not happen the first 5 years of the mission, we may see a couple more as the Moon's orbit slowly shifts.
Here is a movie from the flight operations team showing the double transit.

On August 31, 2016, SDO will perform the EVE field of view and HMI/AIA Flatfield Maneuvers. More on that later.

Saturday, August 6, 2016

You Never Miss Them 'TIl They're Gone!

I had forgotten how nice it was to see the Sun each morning in all of the different ways SDO provides.

It took longer then we expected, but as of the end of the Friday work day, SDO is in science mode and all three instruments are returning science data. AIA is currently taking images with the nominal 8 images every 12 second program but it is running an older version of flight software that is affecting the Image Status Packet. We plan to leave the system in this configuration over the weekend.

It's been a long week for the SDO team and I hope they can return Monday ready to fix the remaining issues.

Thanks to all who helped SDO to return to operations.


Tuesday, August 2, 2016

Lunar Transit this Morning

SDO had a lunar transit this morning from 1113-1207 UTC (7:13-8:08 a.m. ET). The spacecraft did not go back into Science mode at the end of the transit. SDO FOT members are looking into the issue.

Wednesday, July 20, 2016

EVE Cruciform today

SDO will perform an EVE cruciform maneuver today. From 1700-2152 UTC (1:00 p.m.-5:52 p.m. ET), SDO will rock up and down and back and forth as a calibration maneuver. During this time the AIA and HMI images may be blurred or blank.

Wednesday, July 13, 2016

Momentum Management Maneuver Today

SDO will perform momentum management maneuver #26 today from 1945-2000 UTC (3:45-4:00 p.m. ET) today. Science data is not returned during the maneuver.

Wednesday, July 6, 2016

HMI Roll Today

We are starting the July maneuver season. Today is the HMI roll maneuver from 1500-2000 UTC (11 am ET to 4 pm ET). During the roll the Sun will appear to flip in the NRT data. This data is used to maintain the calibration of HMI and to study how round the Sun is.

Friday, June 24, 2016

Telstar 401, A Ghost of Space Weather Past

Earlier the week we received our conjunction report that lists satellites that will pass close to SDO. Our inclined geosynchronous orbit means there aren't a lot of satellites near SDO, but every couple of months one will come within 20 km (12 mi) of our spacecraft. This week saw the return of Telstar 401 to our list (see the picture at left.) Telstar 401 is a large telecommunications satellite that failed January 11, 1997, and has since drifted around the geostationary belt of satellites. This is not a small satellite, the solar panels stretch about 60 ft across. It's good to know the other satellite is around, but it would be better if was moved to a graveyard orbit well outside of the geostationary belt.

It is possible that Telstar 401 failed because of the activity created by a coronal mass ejection that rose off the Sun on January 6, 1997. (The gray picture at left shows what the CME looked like at 1850 UTC on that date.) The CME is the white arc moving down from the occulting disk. It is called a halo CME because we see it as a ring around the Sun, which means it is heading straight towards Earth!

The impact of the CME was not very dramatic when it reached Earth a few days later. But the energies of the radiation belt protons and electrons were increased enough that they caused an electronic component to arc and fail. There were several attempts to revive Telstar 401, but it was eventually declared a loss.

According to the Union of Concerned Scientists, there are almost 500 satellites currently operating in geosynchronous orbits about the Earth. Most of them are in the geostationary belt that allows them to appear stationary in the sky. There are about 100 defunct satellites in graveyard orbits further away from the Sun. But it is the failed satellites and spent boosters that blunder along and show up on the SDO conjunction report every month or so.

Telstar 401, a true ghost of space weather!