Again the USA 144 (Misty-2) Decoy brightness variability, with another specular glint

Since about a year, I am regularly targetting the enigmatic object (related to what was probably the Misty-2 stealth satellite launch) we call the USA 144 Decoy (99-028C) as part of a long term monitoring of the brightness variability of this object. It shows a slow sinusoid brightness variation with a periodicity of tens of seconds. This period of variation slowly evolves over the course of months.

On the night of September 5-6 I captured a series of images again (between 23:11:22.30 - 23:16:32.35 UTC, Sep 5, 2010) allowing the construction of a curve. Below is the diagram: I find it best fits a periodicity of 60 seconds:

click diagram to enlarge

Earlier period determinations were:

20 Jul 2010: 61 seconds (see here)
2-9 Mar 2010: 88 seconds (unpublished)
19 Nov 2009: 62 seconds (see here)
25-27 Aug 2009: 71 seconds (see here)

I should actually revisit the two determinations (Aug 2009, Mar 2010) that are well off from 60 seconds to see whether I didn't make mistakes there.

As can be seen, I again captured a solitary anomalous glint produced in the "valley"part of he curve. Something very similar happened earlier on July 20th. Both glints happened near a brightness minimum. Below is imagery of the latest glint from September 5 (showing one image before the glint, then the glint image, and an image after the glint), and a comparison diagram of the July 20th and September 5th glints:

click image to enlarge

click diagram to enlarge

These spikes are quite specular in character, and suggest there is a flat mirroring surface attached to the object on (if the slow brightness variation of the object is due to exposure of long versus narrow sides) one of the narrow sides.

Chasing satellites through clouds and unusual brightness behaviour of the STSS Demo 2

The evening of Saturday-Sunday 20-21 February saw a very dynamic weather situation. Fields of clouds came and went very rapidly: the sky could go from clear to clouded to clear to clouded again in a matter of minutes. It made it a big gamble whether a particular object would eb visible or not.

As it came to be, I hauled a nice batch of positions on several objects: Lacrosse 5 (05-016A), the Lacrosse 5 r/b (05-016B), the STSS Demo 2 (09-052B) and the NOSS 3-2 (03-054A & C) duo. I also photographed the NOSS 3-4 duo but the image was too much hampered by cliuds tp reliably measure it. I lost amongst others Lacrosse 4 and the STSS Demo 1 to clouds (the latter a pitty, as it was predicted to pass right through the Pleiades).

Most of the images have some clouds on them: some extensively. Below are a few pictures: from top to bottom they show the Lacrosse 5 r/b amidst clouds; The NOSS 3-2 duo passing between the Pleiades and the Hyades; and the STSS Demo 2 passing near capella and the three Goats:

click images to enlarge

The STSS Demo 2 appears to show an unusual brightness variation in the first 2 seconds of the trail (the left part of the trail in below negative image), consisting of what appear to be a series of even spaced modest glints. Note the dashed appearance of the first part of the trail:

click image to enlarge

Below is the brightness profile over the trail (grey small crossmarks are individual pixel values, the solid line is a 3 point average), and below that is a graph of the time between brightness maxima visible in the profile.

click diagrams to enlarge

Note in the second diagram how the time between maxima is very constant, at about 0.13 seconds, during roughly the first 2 seconds . After that, it begins to wildly vary. As the first diagram shows, the amplitude of the brightness variations is larger in those first 2 seconds too. In fact, after those first two seconds the variation is largely or completely random pixel variation.

The first 2 seconds of the trail are quite different in character from the rest of the trail though: a clear constant, larger amplitude pulsing behaviour. This is very interesting. A second image obtained on the STSS Demo 2 during the same pass showed a quite constant brightness.

Off to a good start: a GOCE and a Lacrosse 2 flare

2010 started off well with a very clear evening of January 1st. I observed GOCE (09-013A), the Lacrosses 2 & 3 (91-017A & 97-064A), the tumbling NOSS 3-4 Centaur rocket (07-027B), and the HEO objects USA 179, 184 and 200.

I was treated to two small flares: one by GOCE (09-013A) and one by Lacrosse 2 (91-017A).

The GOCE flare was a mild one to about +3, at 17:32:58.0 UTC. It was caused by the 67.5 degree panel. The time of the flare (accurate to 0.1s) yields an angle of 93.2 and tilt of 66.3 with a nominal mis distance to the theoretical flare path (angle 90 degrees, tilt 67.5 degrees) of 19.4 km at the time of observation (and closest approach to 17.1 km 1.2 seconds earlier at 17:32:56.8 UTC).

So far, all the GOCE mild flares I observed were with an angle ~93 degrees. The distance to the nominal flare path of this one was much less than for the three flares previously observed by me, but that doesn't seem to have much influence on the observed flare brightness: they were all around +3 magnitude.

Below are the picture, the derived brightness profile, and a depiction of the flare path geometry based on Simone Corbellini's Visual Sat-Flare Tracker 3D software.

click images to enlarge

Unexpectedly, I also captured a brief (<0.5s) flare/glint by Lacrosse 2 (91-017A) at 17:56:58.4 UTC. Below is the image and the resulting brightness profile:

click images to enlarge

More flares by GOCE!

After my observation of GOCE (09-013A), ESA's Gravity field and steady state Ocean Circulation Explorer, mildly flaring at 19 November (see here and here), I observed it flaring again on two other occasions: November 25 and November 26th.

Times of these new flares were 17:14:43.6 UTC (Nov 25) and 17:10:25.8 UTC (Nov 26). The November 25th flare was again of about +2.5 magnitude. The November 26th flare had cloud interference.

Below are two images of the November 25th flare (one full, in negative to show the very faint non-flare part of the trail; and a detail of the flare part), and the resulting brightness profile. FWHM of the flare peak is ~0.4s.

click images to enlarge

click diagrams to enlarge

The observation of the flare of the 26th was hampered by clouds. In fact, I only just managed to photograph the satellite at culmination through a temporary gap in the cloud cover. Still, the image (see below) clearly shows it flaring again, quite similar to how it did the evening before:

click images to enlarge

Note that these flares are probably cases where my observing locality was not that near to the central flare path. In fact, the theoretical flare path for the solar panel that probably caused these two flares of the 25th and 26th was over the UK, not the Netherlands.

I have to wait untill I have the opoortunity to observe a flare when the theoretical center of the flare path is closer to my location. Earliest opportunity, weather willing, is next Sunday evening.

Yesterday's GOCE flare modelled

After measuring the image I obtained of yesterday's GOCE flare, I determined the flare time to be 17:40:34.9 UTC (Nov 19).

Using Simone Corbellini's excellent Visual SAT-flare Tracker 3D software I found the following observational geometry:

---------------------------------------------------
SAT ID #34602 (09013A) GOCE
ORIENTATION TYPE #4: V-Sun ROTAX-DEC: 0 ROTAX-RA: 0
NUMBER OF SURFACES: 1
M#01 - 19/11/2009 17h40'34" - UM1 >>> .8839;77.1618;1
---------------------------------------------------

Note that the angle sun-craft-observer is close to zero (0.9 degree): sun, observer and craft are on one line.

In below graphic representation from Simone's software, the green line is the observed flare path over Earth's surface:

click image to enlarge

Knowing that the spacecraft has a fixed attitude towards the sun (see the ESA website), and Octagonal shape (meaning reflective surfaces at angles 22.5 and 67.5 degrees available), I find the following theoretical flare model:

SATELLITE SURFACE MODEL
---------------------------------------------------
SAT ID #34602 (09013A) GOCE
ORIENTATION TYPE #4: V-Sun ROTAX-DEC: 0 ROTAX-RA: 0
NUMBER OF SURFACES: 2
M#01 - 19/11/2009 17h40'34" - UM1 >>> 0;67.5;1
M#02 - 19/11/2009 17h40'35" - UM2 >>> 0;22.5;1
---------------------------------------------------

click image to enlarge

This suggests the tilt of my observation is 10 degrees off from the nominal theoretical tilt: either the true tilt is 10 degrees different, or (and I favour that, as it is most likely) modest flaring is still visible 10 degrees on either side of the tilt axis.

In the latter case, closer approaches to the central flare path potentially might result in much brighter flares compared to yesterday's. I'll have opportunities to check that the next 3-4 days, if weather cooperates...especially the evening of 21 November might then see a potentially very nice flare for me.

Yesterday's image of the flare/glint I posted came out a bit dark after conversion to jpg. Below is a lighter version and a larger detail image.

click image to enlarge

Flaring Keyhole USA 161

Yesterday evening/early night was a night with intermittent very clear skies, and large cumulus fields roving the skies. I was lucky though with the selected targets, although some narrowly escaped the roving cloud fields only. I observed 3 Keyholes (USA 129, USA 161 and USA 186) and Lacrosse 3.

USA 129 (96-072A) was imaged low in the sky in a small gap between clouds. USA 186 (05-042A) was imaged in twilight and the trails were rather faint. It briefly flared to mag. -1, before the camera was open, at roughly 22:59:50 UTC.

USA 161 ((01-044A, a Keyhole high-resolution optical reconnaissance satellite, like the other two USA objects mentioned) also briefly flared to -1 a few times. It did so twice while the camera was open, at 23:28:13.40 UTC and 23:30:17.15 UTC, resulting in the pictures below:

(click images to enlarge)

The second image yielded this brightness profile, with the flare saturating at the peak:

(click diagram to enlarge)

Keyhole USA 161 flaring

On the night of April 1-2, the Keyhole optical satellite USA 161 (01-044A) flared brightly to mag. -2 just after shadow exit. I shot a whole series of images (yielding 7 positions), of which this is the first (exposure starting a few seconds after flare maximum):

(click image to enlarge)

The same evening I also captured the Keyhole USA 129 (96-072A). HEO objects imaged were the SIGINT USA 200 (08-010A) and two brief glints by NOSS 2-3A (96-029A). The Russian Kosmos 2392 (02-037A) was captured as a stray on the USA 200 images.

Iranian Safir 2 r/b still slowly flaring

Yesterday evening, the atmosphere was very dynamic, with short clear spells repeatedly giving way to fields of clouds.

Nothwithstanding these conditions, I managed to image the Keyhole USA 129 (96-072A) again, plus the Iranian rocket booster Safir 2 r/b (09-004B) that launched OMID in February. I imaged it earlier in the morning of 7 March.

At that time, it showed bright flares in a slow pattern. It is still doing so, as yesterday evening's images show. The time between the bright glints is slightly less than it was early this month. I determined a 31.7 second interval between two of the glints, with glint times at (March 29 UTC):

19:57:19.5 UTC
19:57:51.2 UTC

On March 7, the determined glint interval was 33.25 seconds.

Below are the two images of last evening, plus the brightness curves. The glints appear to be slightly asymetric, with a slightly more shallow fall-off of the brightness after the glint maximum:

(click images to enlarge)

More flashes from the Iridium 33 wreckage

Yesterday evening, after observing the exciting ISS-Shuttle duo pass (see previous post), I tried to observe flashes from the Iridium 33 wreckage (97-051C) again. Simone had provided some experimental predictions and asked for verification.

The Iridium 33 wreckage did flare: two very bright flashes (both around mag. -1) seen naked eye, and two fainter ones (+4?) found on a photograph. They were off from the experimental predictions, but still cool!

The two -1 naked eye flashed were observed at 17 March, 20:06:56 ± 1s and 20:07:02 ± 5sUTC. The two photographic fainter flashes/glints occurred at 20:07:15.7 and 20:07:20.4 UTC. The time between the latter two is 4.7 seconds, and the first two (the naked eye ones) within their timing uncertainties fit a similar 4.7 second period.

The image with the two faint photographic flashes is below:

(click image to enlarge)

Iridium 33 wreckage photographed, with +4 glint

This evening was quite clear, and I decided to employ my new Canon EF 100/2.8 USM Macro lens to image a pass of the Iridium 33 main wreckage (97-051C). This lens has a bigger aperture than the EF 50/2.5 Marco I normally use, and hence is better for faint objects.

I was lucky and not only captured the very faint, irregular trail of the Iridium 33 wreckage: but also a short glint to mag. +4 at about 19:29:51 UTC (15 March), which I also observed with the naked eye.

The image is below. The inset shows the short glint, close to the end of the trail.

(click image to enlarge)

An Iranian rocket (Safir 2 r/b)

Weather finally allowed me to observe one of the new Iranian objects from the February 2nd launch. It concerned the rocket booster from the launch, the Safir 2 r/b (09-004B).

Conditions were not perfect (somewhat hazy), but the rocket booster was well visible and I captured it on two images (see below). It showed a clear very slow amplitude brightness variation (amplitude >20 seconds), going between mag. +3 and near-invisibility for the naked eye (> +4). Around the brightness peak it gives a short bright glint. Both my photographs captured such a glint.

(update) Based on the two pictures, and assuming I didn't miss a glint in between them, the glint period is 33.25 seconds, with glints at:

7 Mar 2009 04:26:12.60 UTC
7 Mar 2009 04:26:45.85 UTC

Below the two pictures (as usual, Canon EOS 450D @ 800 ISO + EF 50/2.5 Macro @ F2.8), and the brightness profiles for these trails.

(click images to enlarge)

The glinting behaviour of USA 32 (88-078A)

The year 2009 has started with a period of frost, and hence clear skies. I observed on January 6 and 9 and this evening (the 11th), catching a batch of objects: Lacrosse 3, USA 32, and various NOSS duo's.

The image of USA 32 (88-078A, a SIGINT satellite launched in September 1988) of this evening very nicely shows the glinting behaviour of this satellite. Along the trail, small bright dots (= very short glints) can be seen at regular intervals. They are indicated by the downward pointing arrows in the image (a 10.05 second exposure taken with my Canon EOS 450D and EF 50/2.5 Macro lens at F2.8):

(click image to enlarge)

Below is a brightness profile derived from the pixel brightness along the trail. The same peaks as indicated by the arrows in the photograph, show up well and are labelled A to H:

(click image to enlarge)

Analyzing the position of the glints, shows the following sequence:

1) a series of 4 or more glints at a regular 1.20 second interval;
2) followed by 2.0 seconds of no, or much less bright glints;
3) followed again by 4 or more glints at a regular 1.20 second interval.