The Nanosail UNID (10-062X) and Lacrosse 5 brightness variation

When NASA's experimental solar sail Nanosail-D was launched by a Minotaur IV rocket in 2010, it was not the only object this launch brought into space. A number of other, classified objects were part of the same launch.

Now Nanosail-D has decayed, four of these objects (RAX, OREOS, FASTSAT, FAST 1) are being tracked by amateur trackers. One additional object of the launch that is being tracked, however cannot be identified reliably with one of the payloads so far. It could be a payload, or a rocket part from the launch. Dubbed the 2010-062 UNID (10-062X) or "Nanosail UNID" by amateur trackers, it is an object near magnitude 4-5, stable in brightness.

The footage above (WATEC 902H + Canon EF 2.0/35mm lens) shows it passing through the tail of Uma (bright stars are epsilon Uma and delta Uma) on April 1st 2012.

I also filmed Lacrosse 5 (05-016A) that evening. The erratic brightness behaviour of this satellite has featured before on this observing blog. Using footage from the April 1st pass and LiMovie, I reconstructed the brightness curve below, showing a  flare at 20:09:14 UTC and a general quite irregular brightness behaviour with what looks like several small peaks. At 20:09:30 UTC, it appears to do it's typical "disappearance trick" again, dropping rapidly in brightness in just a few seconds of time (note: shadow entry was not before 20:12:00 UTC). The profile is very similar to profiles for Lacrosse 5 which Philip Masding previously obtained, also showing the "disappearing trick" being preceeded by a flare.

click diagram to enlarge

The video footage this curve is based on, is this footage (shot with a 12mm wide-angle lens):



More objects were observed the past few nights. Among them USA 129 (96-072A) and Lacrosse 4, while CCD imagery of Prowler (90-097E)  using the "remote" Rigel telescope of Winer observatory was obtained again as well.

Lacrosse 5

For those arriving here through the link with Thierry's imaging of Lacrosse 5 on Spaceweather: a discussion of the Lacrosse 5 "disappearance trick" including a video of such an event, can be found here.

The Lacrosse 5 "disappearance trick" captured on video

Note: the video below was featured (with my permission) on Spaceweather.com. 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)

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.

The Lacrosse 5 (05-016A) "disappearance trick": comparison of different occasions

Note added 13-11-2011:  visitors coming here through the link on Spaceweather.com, please read this story here first (click link) as there seem to be misunderstandings of what the video shows.


I am behind with reporting my observation activities over the last two weeks. Hereby a quick report however on one part of the observations: the Lacrosse/Onyx 5 (05-016A) SAR satellite.

Amongst the other Lacrosses (4 still in orbit, including Lacrosse 5) Lacrosse 5 is different in that it displays sudden and prominent brightness changes: from very bright (typically +1.5 or better) it goes to naked eye (near) invisibility, with a magnitude drop of at least some 3 magnitudes, in a matter of seconds. After that, it sometimes stays faint during the remainder of the pass: and sometimes it brightens up again after a while, sometimes followed by a second fading event.

This behaviour was coined the "disappearance trick" by me a few years ago. Although the earlier Lacrosses show some brightness variation as well, none shows it so clearly as Lacrosse 5, meaning something in the design of this satellite is different from its predecessors.

I have now been able to capture the satellite in the event of doing the "trick" three times: on 26 September 2009 during the BWGS meeting at Leo's place in Almere; and in the last two weeks on 24 February and 1 March 2010. The pictures and derived brightness profile of 26 September 2009 can be seen here: below are two pictures of the recent 24 February and 1 March observations.

click images to enlarge

The captured 24 February occasion was a case of Lacrosse 5 re-appearing and then disappearing again for a second time during the same pass.

I have combined the brightness profiles of all three events mentioned above into one comparison diagram. In all cases the curves are composites of 2 or 3 images taken during the pass in question (hence the non-continuous nature of the curves: the gaps are periods inbetween two pictures with no data recorded). The shown lines are 15-point averages to the pixel brightness along the trail.

click diagram to enlarge

It is clear from this comparison that the character of the brightness drop is not the same on all occasions. The 26 September 2009 event for example is more steep and sudden than the more gradual 24 February 2010 event. The 26 September 2009 event on the other hand compares relatively well to the 1 March 2010 event, the latter being perhaps slightly less steep.

Another thing notable is the suggestion of a omni-present brief shallow dip in brightness preceding the "disappearance" event by some 15 seconds (it can be seen near the 10 seconds mark in the diagram).

It is still difficult to make sense of this all. What are we seeing here? 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?

Phillip Masding has also probed the strange brightness behaviour of Lacrosse 5: his page with results is here and can be used as a comparison to the results I report above.

The Lacrosse 5 "disappearance trick", and a BWGS meeting

On Saturday 26 September, a small number of BWGS satellite observers gathered at the house-boat of Leo Barhorst (Cospar 4253) at Almere. Present were, besides Leo Barhorst, BWGS president Bram Dorreman and me. A number of active BWGS observers alas could not come, hence the rather small group this time.

In the afternoon we exchanged some information, looked at some software, my collection of "black space program" mission, launch and unit patches, and Leo's collection of space-related postal stamps. I demonstrated how I astrometrically measure my satellite photographs for positions, and how I get brightness curves from an image.

The plan was to try some joint observations that evening (we could stay for the night at Leo's boat), and as it was sunny, we started preparations in the early evening. I took below photograph of Leo (seen frontal) and Bram (seen on the back) while they were making their preparations

click image to enlarge

The sky was not perfect (and would progressively deteriorate later that evening). From a small green a few tens of yards from Leo's boat, we started by watching Iridium 80 flare to mag. -3.5 close to epsilon Cyg in the eastern wingtip of Cygnus. I took the picture below, a 10-second exposure with the EF 100/2.8 Macro USM:

click image to enlarge

Immediately after that I rushed to re-aim the camera and capture the USA 144 decoy (99-028C) passing close to vega in the next minute. Predictions had put the track just west of Vega, and while Bram and Leo were watching there with binoculars I made a series of images. Strangely enough, Bram and leo did not pick it up: and the reason was, after a look at my photographs, that it passed east of Vega, not west! After a puzzled "huh?!?" it dawned upon me: the coordinates of my prediction software were still set on my Leiden locality!

Next up were the objects related to the recent launch of a Russian Meteor weather satellite. Bram and Leo indeed picked one up with their binoculars.

Shortly after that, we watched a nice pass of the SAR Lacrosse 5 (05-016A) with the naked eye. As we watched it, it did it's infamous "disappearance trick" again. It did so during an exposure, that captured the quick loss of brightness very well. It was the first time I imaged the phenomena with my Canon EOS 450 DSLR. It yielded this very nice diagram of the brightness variation (constructed from two images):

click image to enlarge

Note how quick the brightness drop is (it takes a mere 4 seconds) and how sharp the turnpoints in the diagram are.

Next up were passes of the KH-12 optical reconnaisance Keyhole USA 186 (05-042A), which briefly attained naked eye visibility and was of course photographed; and the NOSS 3-3 duo (05-004A & C) which were faintly visible to the naked eye as they crossed Cygnus, and yielded two very fine pictures, one of which is below:

click image to enlarge

Note the difference in brightness between the A and C components. (note: I mistakenly labelled the C component as 'B' in the image...)

After this, Leo and Bram observed the NOSS 3-3 rocket, which is a flasher. As the sky quality rapidly deteriorated, we called it quits after that and went inside to reduce the observational data.

It was nice to meet and observe together. Leo was a perfect host, and his cat Bankie kept my feet warm later that night.