Wednesday 30 November 2011

Observing Fobos-Grunt on 30 November

It was clear this evening, and the Russian Mars/Phobos probe Fobos-Grunt (2011-065A) stranded in Low Earth Orbit made two visible passes which I both observed.

The first pass was in deep twilight, 16:08 UT with the sun only 5 degrees below the horizon. The sky was still bright blue and only the brightest stars (Altair and brighter) were visible. Nevertheless, Fobos-Grunt was easily visible by the naked eye, becoming clearly brighter than Altair around and after culmination at 45 degrees elevation in the south. It was very fast and showed no sign of brightness variation. A very fine view!

It made a second pass at 17:40 UT, plunging into the earth shadow at 25 degrees due west. I captured it on a photograph when it was at 20 degrees elevation, close to alpha Oph (brightest star in the image):

click image to enlarge

The lens used was the SamYang 1.4/85 mm and because of the low elevation and city environment, I kept the exposure short to 5 seconds. Due to a different phase angle compared to the earlier pass, the space-probe was faint, near +4.

I also tried to video it again like two nights before (see video in my previous post). This time less succesful, due to a case of Murphy. A cable came lose just at the moment supreme, and in the haste to attach it again, the camera was moved and then pointed to the wrong star.....

Monday 28 November 2011

Footage of a Fobos-Grunt pass

The footage above was shot by me this evening, and shows the Russian space probe Fobos-Grunt (aka Phobos-Grunt or Phobos-Soil), 2011-065A.

Fobos-Grunt was supposed to go to the Martian moon Phobos for a sample return mission. Instead it got stuck in a Low Earth Orbit, due to a rocket engine malfunction. It is now expected to re-enter into the earth atmosphere early to mid  January.

This footage was shot from my girlfriend's appartment at the second floor of our appartment building: only there was I able to point low enough in the sky. The footage shows the space-probe at an elevation of less than 15 degrees over the western horizon. It enters earth shadow at the end of the 50 second clip.

Sunday 20 November 2011

NOSS 3-1 A & C no longer a pair, and Lacrosse 3 is missing

On November 14th and 15th, Alan Figer from France first noted that one of the objects of the NOSS 3-1 pair (2001-040 A & C) was missing. Following up on his message, I could confirm this the next evening, using photography and video. Only one object instead of the usual close pair of two was visible:

Above is the video footage that was shot by me. What turns out to be the A-component can be seen crossing Lyra (bright star is Vega. The glow in the lower left corner is from a nearby lamp), but no C component is to be seen in this video segment (nor was it for one minute before and 3 minutes after this segment). Next, Derek Breit missed it as well in a window of 8 minutes centered on the A object pass, and so did Brad Young.

Over the past few days, two possible obervations have been made of the missing C-object, now well away from the A object, by Brad Young and Bill Arnold.

The break-up of the NOSS 3-1 pair probably means it had reached end of mission. It is interesting to see that some of the older NOSS pairs (and one trio) do still  maintain their pair bonding though..

Lacrosse 3 has gone missing - perhaps deorbitted

Another satellite, the 14 year old SAR satellite Lacrosse 3 (1997-064A) has gone missing in a more serious way. It has not been seen since early October. Several observers including me and Pierre Neirinck have done plane searches but so far, it hasn't been recovered. So it has either manoeuvered into a completely different orbit, or has been de-orbitted. If the latter is true, this possible de-orbit comes half a year after the de-orbit of Lacrosse 2 late March 2011. It leaves two remaining Lacrosses  in orbit (Lacrosse 4 and 5).

Sunday 13 November 2011

The Lacrosse 5 "disappearance trick" captured on video

Note: the video below was featured (with my permission) on Unfortunately, it was initially suggested there (and this definitely did not come from me) that the discussed "disappearance trick" is a deliberate "stealth" feature of this satellite.
It almost certainly is not: it is something brough about by accident from something specific in the satellite design.

I also want to make clear, as it kept popping up in the YouTube comments (which I have now disabled), that this is not the moment the satellite disappears in earth shadow! The drop in magnitude happened at 17:35:20 UTC: shadow entry was much later, 17:38:55 UTC.

The video above was shot by me Friday evening (11 Nov). It shows Lacrosse 5 (2005-016A), the latest of the Lacrosse SAR satellites.  It was launched in 2005. In the movie, it is doing it's infamous "disappearance trick" (also note the old Russian rocket stage visible in the second part of the footage).

The brightness behaviour of this satellite is different from that of the previous Lacrosse satellites. Apart from that it is brighter overall and a bit yellowish in colour (the others are distinctly orange-reddish), it shows a variable brightness behaviour that the other Lacrosse satellites do not show (or at least not to this extreme extend).

Lacrosse 5 can sometimes drop several magnitudes in brightness, typically from +1 (easy naked eye) to +5 or +6 (naked eye invisibility or near-invisibility), in a matter of seconds.

After observing this a couple of times, I coined it the "disappearance trick", a term that has stuck in the amateur satellite observer's community.

While many satellites can flare briefly (and the Lacrosses do), this opposite effect of one suddenly dropping in brightness other than due to normal phase angle changes or entry into earth shadow (which is not the case here!!!), is not quite common. And Lacrosse 5 does it that frequently, that it stands out.

Normally, when a satellite or spent rocket stage shows sudden changes in brightness, it is due to either:

a) the satellite entering earth shadow;
b) the satellite is tumbling.

Both are not the case here. These "disappearance tricks" of Lacrosse 5 happen well before the point of shadow entry. In addition, the behaviour is not the typical "flashing" behaviour of a tumbling or spinning satellite. There is no periodicity, and the drop in brightness happens after a long period of stable brightness.

The behaviour is interesting, because the sister ships of Lacrosse 5 (the other Lacrosses) do not typically show this behaviour. The implication is, that Lacrosse 5 is different in design than Lacrosses 1 to 4.

I have photographically documented the phenomena several times, including brightness curves (see here, and a comparison of several curves showing the phenomena here, featuring the comparative diagram shown below).

click diagram to enlarge

Philip Masding has been documenting the phenomena as well, his results can be seen here. His curves also show, and I have seen this happen as well, that Lacrosse 5 can sometimes "re-appear" (and, as I have seen occasionally, next "disappear" again...).

One point is, that we so far cannot find a clear pattern in this all. The satellite does not seem to do this at specific phase angles for example.

We are still at a loss to explain this behaviour. Please note: we don't think it is an intentional "stealth" characteristic. Yet it must have something to do with the satellite design or operation.

Is it a matter of strongly differing reflectance properties of the satellite body with illumination angle? Is it some brightly reflecting appendage on the satellite disappearing from view? Is it a dark appendage on the satellite starting to block view of the illuminated satellite body, or casting a shadow on it? Is it due to some moving part of the satellite, e.g. a moving dish antenna?

We simply do not know. And it is giving us a nice puzzle.

The photograph below, taken in addition to the video footage above, shows Lacrosse 5 in the bright phase of Friday's trajectory.

click image to enlarge

Apart from Lacrosse 5, I observed a couple of other satellites last Friday, including the NOSS 3-5 duo (11-014A & B) and USA 32 (88-078A)

Friday 11 November 2011

If rescue fails, Fobos-Grunt will reenter soon

As new attempts to contact the probe failed, the future is looking increasingly grim for Fobos-Grunt (aka "Phobos-Grunt" and "Phobos-SOIL"), the Russian space probe launched on 8 November that should have gone to the Martian moon Phobos for a sample return mission, but instead got stuck in Low Earth Orbit.

The probe is currently stuck in a very low orbit measuring 207 x 339 kilometer after it's propulsion unit apparently failed, failing to lift it into a GTO (and from there an interplanetary trajectory):

If the probe isn't revived in due time - and the Russsian operators are still frantically trying to do so - it is doomed. With an orbit at this low an altitude, it is a short matter of time before it comes down again - another case of an imminent uncontrolled reentry of a very large satellite (over 13 metric tons, including the fuel). How much fuel is onboard is not clear to me: different media sources quote quite different amounts, but all amounts quoted are in terms of several tons, with several sources settling for 7 tons (see also here).
As pointed out here by Anatoly Zak, seizable chunks of the probe could survive reentry, and survival is certainly expected for the actual Fobos sample return capsule (which was designed for reentry).

Reentry estimates

Estimates of when Fobos-Grunt  will come down are a bit complicated. Ted Molczan has noted that over the past day, the orbital evolution was unusual - Ted points out that if the last two orbit releases are not faulty (a  possibility), it means that either the probe is manoeuvering (which from all the negative statements by the Russians in the press seems unlikely) or - more likely - has started to vent fuel since yesterday. As a result, it might have gotten a very mild orbital boost (the leaking fuel acts like a small rocket engine).

Before this unusual behaviour started, orbital elements 11314.14749491 to 11314.77184893 and Alan Pickup's SatEvo software with current solar activity levels suggested a nominal reentry time no later than early January 2012. SSC meanwhile predicts reentry for November 26th, 2011. The current unusual orbital evolution - if real - might change things a bit, but eventually it will come down.

This means it will likely come down somewhere over the next few weeks or months if the operators cannot revive it over the next two weeks. With an orbital inclination of 51.4 degrees, it can come down anywhere between 51 N and 51 S latitude.

There has been a call out to observers to observe the probe - it's brightness behaviour can yield clues as to whether it is starting to tumble, e.g. because of the suspected fuel venting. So far, observations by Brad Young and Michael Murphy from the US suggest the probe is stable in brightness with no sign of tumbling (see here and here).

Unfortunately, the probe is currently not visible from NW Europe where I am located: it makes passes near midnight, completely in shadow.

First light of my WATEC camera - footage of Lacrosse 5 and the NOSS 3-4 duo

For quite a while, I have had a wish to add video to my observing techniques. That moment is now there.

During last October's Draconid meteor campaign, I was introduced to working with WATEC 902H camera's (see my previous post here), and discovered it was not that technically complicated after all. So when I saw one offered for a very good price in a clearance sale in October, I bought one.

The WATEC 902H is a sensitive surveillance camera, which is able to film stars - and satellites- in the night sky. It is small (fits in the palm of a hand).

I still need to add a GPS time inserter (it has been ordered already) for adding precision timing to the video frames. Once that is done, the system is complete.

Meanwhile, I did some test imaging when it briefly cleared last Wednesday evening. Conditions were not optimal: moonlight and a bit of haze. Below are two results, both movies made using a Canon EF 2.0/35mm lens attached to the camera and in both cases the opening shot shows the "dipper" of Ursa minor, with the brightest stars being beta and gamma Umi.

The first movie shows Lacrosse 5 (2005-016A), at one point doing its "disappearance trick":

The next movie shows the NOSS 3-4 duo (2007-027A & C):

The first experiments were a bit more problematic than anticipated. Initially, I tried to feed the video signal from the camera directly into the laptop (and record using the laptop) using an EasyCap capturing device. That turned out to not work that well. My laptop is old and apparently too slow, and too many frames were dropped resulting in movies that did not flow well.

On the advice of Scott Campbell, Kevin Fetter and Greg Roberts, I then added a HDD recorder to the equipment, recording with this device rather than with the laptop. That turns out to work fine, and resulted in the footage above (note: the original movie files are a bit better in quality than these YouTube versions).

I do not intend for video to replace photography at my observatory: I intend it as an augmentation to the photography. Every once in a while, it is nice to have actual moving footage.

Both techniques have their pro's and con's. Video has accurate timing but low astrometric accuracy (due to the low resolution of the imagery). Photography has a high astrometric accuracy, but less timing accuracy (although by now, after much practise my time residuals are usually well below 0.1s). I think the pro's and con's of both techniques largely even out. One pro point of photography, is that it doesn't need a power supply - meaning you can be more mobile.

Apart from using it on satellites, I also intend to employ the WATEC for meteor surveillance (Peter Jenniskens' CAMS system, if I can get the software to work here, which so far turned out to be problematic) and for observing asteroid occultations.

Wednesday 9 November 2011

Another close encounter of a rocky kind....: 2005 YU55

Half a year after the close approach of asteroid 2011 MD (see my images here and here), another one whizzed by the Earth last night. It was 2005 YU55, a 400-meter wide asteroid discovered in 2005 by Spacewatch. It came to within 0.85 lunar distances at 23:28 UT (Nov 8, 2011), with a maximum brightness near +11.

click image to enlarge

Four hours after closest approach, I made the image above, using a "remote" 61-cm F/10 Cassegrain telescope at Sierra Stars Observatory (MPC G68). It is a 30 second exposure starting at 03:21:41 UT (9 Nov 2011), during which the asteroid (moving from right to left) has trailed considerably.

Astrometry from my images has been included in MPEC 2011-V34 (the G68 observations at
09.11922, 09.14006 and 09.32778).