Nanosail-D: a pattern in the Chaos

Earlier I reported on my August 14 observations of the experimental Solar sail Nanosail-D (2010-062L), including a brightness variation diagram derived from one of the images.

Initially, I could not see any clear pattern in it, so I called it "irregular". Next, Alain Figer from France pointed out it was not so irregular after all. His own images from August 16th (URL's here) show a very neat pattern of one major flash, then two secondary flashes, then a major flash again. On his images, the major flashes are 0.73 seconds apart.

Going back to my observations, it turns out it is indeed possible to find a similar periodicity of 0.73 +/- 0.03 seconds. The secondary flashes appear to be 0.73/3 = ~0.24 from these main peaks: in other words, main and secondary peaks fit a ~0.24s pattern.

Below diagram shows it. the lowest line gives the observed peaks, with the red triangles representing the main 0.73s cycle. The yellow tringles point out several secondary maxima at ~0.24s after the main cycle peak; the grey/white triangles point at a hint of a similar pattern ~0.24s before he main cycle peaks.
The upper line shows the modelled behaviour: a main peak (black triangle) each 0.73s, with secondary and tertiary peaks at ~0.24s intervals.

click diagram to enlarge

Nanosail-D flashing rapidly and brightly

As in late May and early June, Nanosail-D (2010-062L), the experimental NASA Solar Sail is making favourable passes again and under favourable conditions becomes bright and is flashing rapidly.

Yesterday evening around 22:50 local time (20:50 UTC) I observed it when it made a near-zenith pass, from SW to NE. While ascending and going through the zenith it was quite bright and an easy naked-eye object, reaching mag. +1.5. It was rapidly and very irregularly, rather nervously flashing.

I shot four images, two of which are shown below: in the first image, the brightness variation is photographically less apparent than it was visually, because the trail is near saturation. It shows the Solar sail passing just below Lyra (Vega in top left) along with a stray, the French Optical Remote Sensing satellite Spot 4 (98-017A, the fainter of the two trails).

The second image, shot while Nanosail-D was getting fainter, shows the sharp flashes more readily.

click images to enlarge

From the latter image, I could derive this brightness variation diagram:

click diagram to enlarge

A large number of sharp brightness peaks can be seen: I count some 26 peaks in a 10.05 seconds time span, the one more prominent than the other. No regularity in the pattern is apparent.

Perseid

Yesterday evening saw very dynamic weather conditions, with the sky going from overcast to cklear to overcast in a matter of minutes. I managed to photograph the FIA Radar 1 (10-046A) and IGS 1B (03-009B).

Then I set up my camera with an Aputure automatic timer and let it take 20 second pictures all night. I did this earlier, to construct a time-lapse showing sky rotation. This time, it was also meant to capture some early Perseid meteors.

I captured one (below), low in the west.

click image to enlarge

Some of my pictures on Wired.com

Wired.com has published a short photographic item about secret spacecraft today.

Two of the images in it were shot by me: a photograph of Lacrosse 3 and one of Mentor 4.

Prowler

Among the family of classified satellites, three stand out as more mystifying than the rest: Misty 1 & 2, PAN, and Prowler.

The latter has long existed in the realm of rumours only. It was launched by Space Shuttle Atlantis on mission STS-38, which was a classified DoD mission launched on 15 November 1990. Officialy only one satellite, USA 67, was launched from the Atlantis payload bay. This is believed to be a geostationary SDS communications satellite, SDS 2-2.

STS-38 mission patch

USSTRATCOM released catalogue numbers (but no public orbit) for three objects connected to this launch: the SDS satellite USA 67 itself (90-097B, 20963) plus two rocket bodies (90-097 C & D, 20964 and 20965).

The latter was puzzling, as it is one too many (see the discussion by Ted Molcan here), This was the start of the idea that a second, unacknowledged object was launched by STS-38 as well.

In 2004 an NBC journalist referred to such a secret payload by the name of Prowler, in a news-item discussing a Senate debate about a classified spy satellite program drawing criticism for massive cost overruns. The same journalist, citing anonymous sources, did so again in 2007.

According to these stories, Prowler was an experimental satellite used for close inspection of other (non-US) satellites in geostationary orbit (see discussion here), reportedly coming to within decimeters of some satellites. There are suggestions that it was a test of technology which, in wartime, could be used to sabotage enemies' space assets. It was also said to employ stealth technologies to evade easy detection.

Meanwhile, US amateur observers Ed Cannon and Mike McCants had discovered an unidentified near-geostationary object in July 1998. As time progressed and more and more ISON and amateur-discovered objects could be identified with specific launches, this one was one of few left unidentified. This in turn led to suggestions that the object in question was the rumoured unacknowledged STS-38 launch, Prowler. It was likely discovered only after its active lifetime ended, and it was put in a disposal orbit (see below).

Since then, a long term analysis by Ted Molczan has strengthened this identification. The object has al the right characteristics in terms of brightness behaviour and orbital behaviour. It currently is in an unusual librating disposal orbit that seems devised to keep it out of reach of Soviet tracking facilities (see discussion in depth by Ted here). In a second analysis, Ted showed that STS-38 indeed had the opportunity to launch this object and some tell-tale clues to that are present in the manoeuvering history of STS-38 Atlantis. The whole history of the object, from launch onwards but also including the final disposal orbit when the stealth character of the object was lost, was designed with low detectability by Soviet tracking facilities in mind (see Ted's discussion here).

The object now resides in a currently 13-degrees inclined orbit librating between 73 W and 136 W, putting it over the eastern Pacific, with visibility from the western United States. Over the past two weeks , I imaged it a number of times, using the 0.61-meter "remote" telescope of Sierra Stars observatory in California. Below is one of the better images, shot on the morning of July 6th:

click image to enlarge

An update on IGS-1B

Along the line of expectations, our tracking data show that the Japanese spy satellite IGS 1B (2003-009B) which malfunctioned in March 2007, keeps coming down (see earlier coverage here and here).

Early July 2011, the perigee had come down to 450 km and the Mean Motion (the number of orbital revolutions per day) is steadfastily increasing as the orbit becames more narrow:





The predicted decay date keeps shifting back and forth, being highly dependant on solar activity. Solar activity has been back to modest the past two months. As a result, the decay date forecast has shifted further away in time.

If solar activity does not increase, forecasted decay will be in late 2013 (SatEvo with current solar flux F10.7 cm = 85, elset 11184.15154535). If it does increase - which is likely, as we are on the approach to a solar maximum - it will be earlier, possibly as early as mid-2012.



Meanwhile, it is interesting to see how the still active sister-ship IGS 1A (2003-009A), launched in the same 2003 launch, is faring. Above diagram shows the evolution of the orbital inclination. IGS 1B's orbital inclination is clearly drifting, consistent with loss of control. IGS 1A's orbital inclination initially was allowed to co-drift with IGS 1B, but then altered in a manoeuvre mid-2008 that brought the inclination up again, to match the other IGS-es in the constellation. As of 2010, it is kept more or less steady, librating around a value of 97.39 degrees, the sun-synchronous value for a 487 x 498 km orbit.

PAN, and the NOSS 3-5 duo

Monday evening was a nice clear evening with a very transparent sky.

I observed the NOSS 3-5 duo (11-014 A & B), which was captured in a very fine image with a stray nearby, the rocket from the Kosmos 1697 launch (85-097B). De double parallel trail above is the NOSS duo, the single trail under an angle is the Russian rocket (bright star near trails is Deneb):

click image to enlarge

I also took opportunity of the transparent sky to target some geostationary objects low in the southeast. Targets were PAN (09-047A) and Mentor 4 (09-001A):

click image to enlarge

Imaging geostationary satellites using a remote telescope [UPDATED]

I have been using the "remote" telescopes of Sierra Stars observatory in California and Winer Observatory in Nevada for some time now to image asteroids (recently, earthgrazing NEA 2011 MD).

The past two days I have used the Sierra Stars Obs. 0.61-meter Cassegrain telescope to make some "remote" images of classified geostationary satellites that are not visible from the Netherlands, but visible from the western United States. It concerned the recently launched SBIRS-GEO1 satellite (11-019A) and the mysterious object (90-097E) that is most likely Prowler, launched in 1990 on STS-38.

Below are the images: as this is a guided telescope, the satellites have created trails on the images. Top image: Prowler. Bottom image: SBIRS-GEO1, plus an unidentified object (UPDATE: the latter object might be the SBIRS-GEO r/b).

click images to enlarge

OT: more imagery of the earthgrazing asteroid 2011 MD

Like yesterday, I used the 0.61-meter F/10 Cassegrain of Sierra Stars Observatory (G68) in California again to image the earthgrazing asteroid 2011 MD, this time a few hours after closest approach.

Below animated GIF was made from three 30 second exposures, spaced 30 seconds, starting at 09:35:01 UTC (28 June).

OT: Close Encounters of a Rocky Kind (2011 MD)

Today, a small asteroid, 2011 MD, made a very close pass by the earth, coming to within a distance of 12,400 km at about 13:30 UTC (June 27). That is well within the distance of geostationary satellites, and even within the distance of GPS satellites in MEO!

This morning, some 5 hours before closest approach, I used the 0.61-meter F/10 Cassegrain of Sierra Stars Observatory (G68) in California, to capture this PHA earthgrazer.

click image to enlarge

This image is a 30 second CCD exposure taken between 08:32:00 and 08:32:30 UTC (June 27, 2011). In these 30 seconds, the fast moving object left a notable bright trail on the image. Star field is in Serpens, image center approximately RA 15h35m57s, dec. +19.441 degrees.

UPDATE: more of my 2011 MD imagery shot on the 28th here.

NanoSail-D: a brief note on how I construct these brightness curves

Some people have asked me how I get the brightness curves from my images. So here is a brief explanation.

On each image, the satellite has made a trail. Start and end times of the exposure are well known, and the start and end of the trail corresponds to these times.

Next it is as simple as using software (e.g. MaximDL, or IRIS) that can read pixel values along a line: let the software read a line that corresponds to the satellite trail on the image! With MaximDL or IRIS, this is as simple as drawing a line over the screen with your mouse, exactly over the satellite trail. The software then reads the pixel values along this line. The resulting data can be exported as a data table.

These data are then read into a spreadsheet I created, that for each data point interpolates the corresponding time (remember that the time of the first and last datapoint in the dataset is known: start and end of the exposure).

Now, this assumes the movement of the satellite on the image is linear. Strictly speaking, the apparent speed of the satellite is not linear. However, with short exposures (10s) that will not be a really big source of error.

NanoSail-D: evolution of the flash pattern during a pass

Yesterday evening at 23:00 CEST I observed a twilight pass of the experimental NASA solar sail NanoSail-D again (see earlier and later observations here).

This pass allowed me to capture a series of brightness curves, which document the evolution of the flash pattern during a single pass, as the looking angle is changing (looking "edge on" aroudn culmination, and then more and more "on the tail"as it is descending) . The change in flash pattern is profound: this is clearly a very complex matter where the flash pattern highly depends on the relative position of the object to the observer.

click images to enlarge

It starts (image and diagram 1) with a lot of irregular flashes, spaced 0.3 - 0.9s apart (average 0.49s but with large standard deviation).

Next (image and diagram 2), a nice semi-regular sinusoid pattern develops, flashes spaced 1.24 - 1.45 s (average 1.33s)

Then (image and diagrams 3 and 4), the period increases, the pattern transforming to a slower sinusoid with peaks first 5.61s apart, then somewhat decreasing again to 4.11s apart (edit: or maybe not: the firts "peak"might be a sub-peak. The valleys seem at similar distance to the previous diagram). Superimposed on this, a shorter cycle of minor subvariation can be suspected, with various periods.

This slower variation in the last two diagrams is why Bram, me and some other observers got the impression, on this and some past passes, of the period almost "disappearing" when NanoSail-D was descending on altitudes of ~35 degrees.

Two of the trail images in a bit more detail: note the difference in flash pattern:

click images to enlarge

NanoSail-D Galore

Yesterday evening, I observed a twilight pass (sun at -7 degrees altitude and a still bright blue sky) of NanoSail-D, the NASA experimental solar sail (see earlier posts here). It passed at 44 degrees in the east, and after culmination became very bright again, flashing to mag. 0.

Because of the bright twilight sky I had to tone down the ISO to 400 and diaphragm to F4.0. The images show the flashing behaviour very neatly, and I obtained two spectacular sinusoid brigthness curves (the second one is from the image shown):

click images to enlarge

The flash period is definitely slightly variable, varying between 1.2 and 1.5 seconds with an average of 1.35 +/- 0.12 seconds.

With the current orbit, decay is projected for mid-August.

note added: click the 'Nanosail-D' label below to see later posts on NanoSail.

Yet more bright NanoSail-D, and an unidentified object from the same launch

Yesterday evening (Wednesday evening) was very clear and saw another fine pass of NanoSail-D (10-062L), the experiental NASA solar sail. As on previous occasions, it became very bright after culmination, while descending to the southern horizon: reaching an easy naked eye magnitude of +0.5. It is still flashing, but trail saturation on the images meant I could not get a reliable brightness variation curve this time. Below are two images: one that shows it just north of the Coma Berenices star cluster, the other shows it passing south of Bootes into Virgo somewhat later (bright star in the top is Arcturus):

click images to enlarge

Tonight (Tuesday evening) I had another pass, a low west pass at 35 degrees altitude this time. And....it was invisible, to the naked eye at least.

On April 27th, Russell Eberst observed an unidentified object that moves in the same orbital plane as NanoSail-D and appears to be "something" from the same launch (see also here). It was subsequently observed by a number of other observers (and perhaps earlier, on March 3, by Greg Roberts), and yesterday I photographed it:

click image to enlarge

Another object observed this evening was Lacrosse 5 (05-016A).

More flashing NanoSail-D, and flaring KH-12 USA 224

A week after my May 24 observations, I observed NanoSail-D (2010-062L) again, the experimental NASA solar sail.

NanoSail-D (image: NASA/MSFC)

As a week ago, it became very bright after culmination, while descending in the south, and was rapidly flashing again. It was easily seen by the naked eye, reaching mag. +1 or possibly +0.5.

In fact it is so bright, that the pixel brightness of the trail reached saturation on two of the three images. The first image (below) did yield brightness information: the resulting curve is shown beneath it. The flash period is irregular, but periods of 0.5s and 1.0s pop up frequently in the diagram (for actual determined flash times, see here. Astrometry on the satellite itself can be found here).

click images to enlarge

As can be seen on the images, the satellite was in a race with an untimely field of clouds (the orangish streaks in the images), staying just ahead of it. Visually, the brightness fluctuation was much more apparent than it is on these images (due to the saturation of the latter): it was very clearly flashing.

Nanosail-D was not the only object flashing. USA 224 (11-002A), the new KH-12 Keyhole launched on January 20 this year, flared too, while passing through the zenith, with flares at 23:48:27.3 and 23:48:31.8 UTC (May 31). The "saddle" and elevated brightness between the two flares is interesting (the trail is notably fainter before the first flash, and subsequent images show it is fainter again after the second flash):

click images to enlarge

This was the second time I imaged USA 224 (The first time was May 24). In addition to USA 224 and NanoSail, I also imaged another KH-12 Keyhole, USA 161 (01-044A), and a Lacrosse SAR, Lacrosse 3 (97-064A).

Nanosail-D: a spectacular show of bright flashes!

Last night I finally was able to capture Nanosail-D (10-062L), the NASA experimental solar sail. It put on a spectacular show, flashing rapidly, becoming an easy naked-eye object after culmination when it reached magnitude +1.

As it gradually brightened from invisibility to naked-eye brightness while passing at 61 degrees altitude due east, it initially flared rapidly, in an irregular pattern, at a rate of 1 to 3 flashes per second. below is the first image, and two other where the trail runs out of the image frame (in haste, I aimed badly when repositioning the camera):

click images to enlarge

When it descended towards the South-Southeast, it became brighter, reaching mag. +1. The flashing pattern became somewhat more regular and slowed down to about one flash per 1.6 seconds. On the image, the trail is quite saturated and hence the brightness variability on the image below is less apparent than it was visually. Visually, the objet was clearly "winking", very cool to see:

click images to enlarge

PAN at its new slot at 45.0 E

Below is an image I shot in the evening of May 9, under not too good conditions (moonlight, and some twilight left).

It shows PAN (09-047A) in its new position at 45.0 E, following the relocation from 49.0 E early May.

Image was shot using the Carl Zeiss Jena Sonnar MC 2.8/180 mm.

click image to enlarge

ISS over the Sun

Late this afternoon (10 May 2011), at 17:29:25 CEST (15:29:25 UTC), the International Space Station (ISS) passed in front of the Sun disc again as seen from the SatTrackCam station, silhoueting the Space Station on the solar disc.

Like on March 24th, I used my small ETX-70 telescope equiped with a Solar Screen Filter, to photograph the event. This time I used prime focus plus a Kenko 2x converter, instead of eyepiece-projection, effectively yielding a f=700mm F/10 system.

Four images out of the series show the ISS silhouted againts the sun, along with several sunspots. Below is a composite image of the four images (showing the ISS four times), plus a detail. The ISS solar arrays are well visible.

click images to enlarge

UNID-I 3 May 2011 = PAN [UPDATED]

On May 3rd, I found two unidentified geostationary objects close to Galaxy 27 and Intelsat 12 (see report and pictures here).

One, UNID-I, was stable in brightness. The other, UNID-II, was flashing. I imaged UNID-I the next night (May 4th) as well, showing it drifting westwards. I might have imaged UNID-II again too, though misidentifying it at that time as Intelsat 12 (except for the occasionally very bright UNID-II, the objects were, due to worse observing conditions, at the edge of detectability).

At that time (see the link above) there already was some suspicion that UNID-I could be the enigmatic classified geostationary satellite PAN (09-047A), caught in the act of yet another relocation.

That suspicion is now confirmed, following additional imaging by Peter Wakelin from the UK on May 8th. Still drifting when I picked it up on May 3rd, PAN now appears to have settled in a new position at 44.9 E, just west of Galaxy 27 and Intelsat 12. It has moved 2 degrees higher in my local sky, to an altitude of 19 degrees.

The identity of the second, flashing UNID, UNID-II which is still drifting westwards on May 8th, is still uncertain. While it is possibly the Indian communication satellite GSat-2 (03-018A) in the act of relocating, Space-Track still lists that object stable in its usual orbit slot placing it at 48 E. So we have something of a remaining mystery to solve there (although in the end, it will probably turn out to be Gsat-2, with Space-Track for some reason failing yet to recognize it is being moved).

UPDATE 09/05/2011: about an hour after I posted this, Space-Track updated the orbit for Gsat-2, showing that UNID-II is indeed Gsat-2, probably on it's way to the graveyard orbit. So, it appears I beat Space-Track to it by several days!

PAN (09-047A) has a history of frequent relocations, making this already enigmatic satellite the more enigmatic. Previous to this early May 2011 relocation, it relocated in early December 2010, an event that I was the first person to detect as well. So far, it has been located at 33.0 E from late 2009 to May 2010 and then was moved to 38.0 E; then to 49.0 E in December 2010; and now to 44.9 E in May 2011.

[UPDATED] Two Unidentified Geostationary Objects on May 3 and 4

May 3 was an unusually clear evening, and I decided to target a few classified geostationary satellites, using the Carl Zeiss Jena Sonnar MC 2.8/180mm.

While imaging the region of PAN (09-047A) and Mentor 4 (09-001A), I found two unidentified objects. Yes: two.

The first object, UNID-I, was discovered close to the commercial geosats Galaxy 27 (99-052A) and Intelsat 12 (00-068A). It was present on multiple images, and the astrometry shows it is stable in declination. It was about as bright as the two commercial geosats, and stable in brightness.

The plot thickened, when a second unidentified object, UNID-II, was discovered just east of the first, just north of the commercial geostationary Syracuse 3A (05-041B). This object was irregular in brightness, alternating between faint and very bright (comparable to Mentor 4 at peak brightness, i.e. about mag. +8).

Below image shows UNID-I near Galaxy 27 and Intelsat 12:

click image to enlarge

The two images below show UNID-II near Syracuse 3A, and the clear flaring behaviour of the UNID.

click image to enlarge

On May 4th, the sky quality was poorer. Nevertheless I tried to recover the two objects, with partial success: UNID-II was captured again on several images.

It had drifted westwards, closer to Galaxy 27 and Intelsat 12 towards the position of UNID-I. The latter was not visible on the images, most likely due to the poor sky quality (Galaxy 27 and Intelsat 12 were barely visible either).

The object showed a clear variable brightness behaviour, being invisible in one image and very bright in the next one taken 30s later. Together with the slowly changing declination, this shows that the object is likely UNID-II, not UNID-I.

Below images were taken 30 seconds apart: the object is bright in one, and invisible in the other:

click image to enlarge

In the series of images, it is present in the following images:

from - to (UTC, May 4th)
---------------------------------------
21:03:02.30 - 21:03:12.35
21:04:02.30 - 21:04:12.35 - very bright
21:05:02.30 - 21:05:12.35
21:07:32.30 - 21:07:42.35
21:08:02.30 - 21:08:12.35
21:08:32.30 - 21:08:42.35 - very bright
21:11:02.30 - 21:11:12.35
21:12:02.30 - 21:12:12.35
21:13:02.30 - 21:13:12.35 - very bright
21:14:02.30 - 21:14:12.35 - very bright
---------------------------------------

As can be seen, there is a clear semi-1 minute periodicity in this.

I have no idea as to the true identity of these two objects. As I could find no trace of PAN (09-047A) near Yamal 202 on my May 3rd images, it is possible that UNID-I is PAN once again relocating.

The presence of a second, tumbling/spinning object, UNID-II, close to it however suggests that more is going on. Finding two UNID's close together is definitely weird and might suggest a connection between the two objects.

UNID-II has a small but clear inclination to it's orbit and appears to be drifting westwards. UNID-I is stable in declination, indicating an inclination close to zero. It might be drifting as well (only more observations will tell, given that I failed to find it on May 4th).

UPDATE 5-5-2011:
Ted Molczan feels UNID-II (the flashing one) could be the Indian commercial geosat Gsat 2 (03-018A) in the act of relocating. UNID-I could indeed well be, as I suggested in my report on Satobs, the classified geosat PAN (09-047A) relocating, according to Mike McCants. I captured the same satellite relocating in December last year: this enigmatic satellite is frequently on the move.