Astronomy

STEREO up and away!

Posted 2006 October 26 @ 06:15 - filed under Astronomy.

The STEREO craft, after a 14-minute delay, launched at 02:52 SAST this morning (Thursday, Oct 26).

Several South African observers attempted to spot the craft and its rocket, but the weather seems to have fouled most attempts.

Observing from Stellenbosch, I started setting up my equipment at 02:20 under clear dark skies. I noticed an ominous cloud bank low on the west and south-west, in the direction of Cape Town, and wondered if Greg Roberts was experiencing cloud.

Just after 02:35, I logged-on to NASA's live video feed of the launch. While sipping a coffee and watching the on-screen action, there was even time for a quick star-party when two policemen on patrol stopped by to investigate the suspicious equipment and obviously clandestine night-time activity outside my house. They got what must have been the shortest introduction to space craft and astronomy ever.

The NASA feed, although not updated very rapidly, was still fascinating to watch. A Java-based application showed various counters and status reports in real-time, accompanied by an array of images, updated periodically, relayed from the launch pad and control room. The image strip on the left shows a closeup of the Delta II rocket's progress.

After the launch, I checked that I had all the paraphenalia necessary and started dark adapting, familiarizing myself with the star-fields which the craft would pass through. The first region was around Beta Tauri, low in the north-east, and I could easily see 8th magnitude stars, which was Greg's earlier estimate of how bright the craft would be.

Thrilled that everything was going well, I sat back and looked about - and only then saw the 50%+ cloud cover. Clouds were inching their way northward, and I could only watch in disbelief as they seemed to cover exactly the path that STEREO would follow in the next few minutes. The cloud blanket soon covered lower Taurus, Gemini's toes, Canis Minor, and Messier 48 - all beacons along the predicted path. The last few degrees above the horizon were perfectly clear. Minutes ticked by, and at 03:30 my optimism finally became realism and I went indoors to e-mail Greg (more about his experiences below).

Shortly after sending the e-mail, I started packing up - only to see that now it was 90% clear again! By this time, around 03:42, the craft was supposed to be somewhere south of Alphard. I realized that it might be too faint to see, but what the heck. I started scanning the region slowly, looking for a faint moving object. Wham, it hit me - a bright satellite, moving in the right direction! Stopwatch in hand, I recorded its position (RA 08h 50.7m, Dec -28:37' at 03:48:07 SAST). The fact that, while fixing the position, I saw another equally bright satellite (moving in the opposite direction) didn't phase me. Neither that it was much too late and far too bright (5.5 mag) for this to be STEREO. I was adamant that I would record a satellite tonight - any one would do, dammit!

Meanwhile, Greg Roberts in Cape Town was using his automated satellite tracking equipment to record the craft's flight. He also had cloud, it turns out:

"Well I had a bit more luck but not sure if I saw the satellites ( never saw them as two items due to small image scale) but at predicted time started my system tracking cloud and managed to see an object at about 8th magnitude that quickly faded as distance from earth increased - I followed it through clouds to about 11000 kms range - it had a slow variation of about 3 minutes when it would brighten by about a magnitude or so. Im reasonably certain it was the rocket - I scanned a bit ahead and behind it but saw nothing- if this was the rocket then the satellite/s would have been even fainter."

With his video observations logged on his hard drive for analysis later today, Greg packed up for the night, after reporting the outcome to George Lewis at JPL.

An email at 04:23 from Lewis reads, in part: "We're getting a downlink through Canberra, though no two-way Doppler data yet -- nominally the Doppler will start at about 2:30 ... Now the pizza's here, so we'll get fed and then start a long work shift. Actually continue it..."

Update, Oct 26 @ 12:00 Bruce Dickson in Johannesburg had high-altitude cloud, washing out anything fainter than 7th mag; Willie Koorts in Wellington had technical difficulties (including a severe hayfever attack!).

Update, Oct 26 @ 15:10 Greg Roberts continues to analyze the data he captured earlier this morning. The image on the right is a frame from the video he acquired, showing what is probably the STEREO rocket, captured at its maximum brightness. "The white fuzzy stuff is cloud," Greg notes. The streaks are background stars, shown as trails because his equipment was tracking the rocket.

Update, Oct 26 @ 19:55 Oleg Toumilovich of Johannesburg also reported cloudy weather, adding that in the late afternoon, temperatures reached 35°C in the shade.

Update, Oct 29 @ 09:36 Greg Roberts has received confirmation that he did, indeed, track STEREO (example image above). David Dunham (IOTA stalwart & STEREO Mission Design Lead Engineer) wrote today:

"Greg Roberts, observing near Cape Town, managed to record several images of STEREO shortly after it emerged from the Earth's shadow a couple of minutes after the injection into the highly elliptical orbit by the 3rd-stage booster. Detailed information about his observations, including several images, are on my Web site at http://highorbits.jhuapl.edu/stereo.htm. The site also contains daily mission status reports, including information about the successful small engineering delta-V maneuvers that were performed about half a day ago, in preparation for the important perigee raise maneuvers that must be performed near apogee, with the first attempt to do that scheduled for Monday. Also there is a short note about the history of the late October launch opportunity, which up to three months before we hadn't considered at all, thinking that it probably wasn't feasible. The 3rd stage rocket is now expected to reenter the Earth's atmosphere on November 6 after 1h UT a short distance north of Grand Turk Island in the southeastern Bahamas, but there is still considerable uncertainty in the longitude where that will really happen. The JPL Horizons Web site has the trajectories for the 3rd stage, and for both of the STEREO spacecraft, with a link provided on my Web site. The spacecraft might be observed again only during 1 to 2-hour periods just before and just after they pass through the Earth's shadow during the next 4 perigees before the first lunar swingby on December 15th keeps them permanently (at least for the next several years) far from the Earth."

STEREO launch

Posted on 2006 August 25 @ 15:05 - filed under Astronomy.

The STEREO pair of satellites is up and ready for launch in the wee hours of Thursday morning.

A Boeing Delta II rocket will carry it aloft at 02:38 SAST from Pad 17-B at Cape Canaveral (Kennedy Space Centre). Soon after launch, the Delta II rocket will disappear below the Cape Canaveral horizon as it speeds eastward. The satellites will separate from the rocket, and then from each other, after which their solar arrays will be deployed. 83 minutes into their flight both satellites should be de-rotated and in a stable orientation.

The rocket and satellites won't be naked-eye targets; Greg Roberts writes:"Initially I expect the STEREO craft to be about +8 magnitude at pass start and probably about mag 11 to 12 by the time they reach a range of about 15000 kms or so but by then twilight may be a problem so they are not exactly easy targets. The trailing rocket should be somewhat brighter."

NOTE: The launch is scheduled for 02:38 SAST, but may be delayed by up to 15 minutes due to unforseen circumstances. Check the STEREO homepage (link below) to make sure. To observe the satellites, visit the JPL HORIZONS website, and select the Target Body as "STEREO-A+3-sigma (spacecraft)". This will allow you to print out an ephemeris for your observing site.

The count-down and launch can be watched online at NASA's ELV Countdown Portal. The STEREO homepage is at http://stereo.gsfc.nasa.gov.

• STEREO mission home page

• Greg's satellite tracking equipment

• David Dunham's STEREO pages

• Comment on this news item in the Forum.

Keywords: STEREO, Greg Roberts, observing satellites

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