Sunday, 28 September 2014

Observing HEO objects

Friday evening I missed the LEO window because of a dinner. When back home near midnight, conditions were dynamic: intermittent clear skies and roving cloud fields.

A HEO (Highly Elliptical Orbit) object called "Unknown 051230" (2005-864A) was well-placed near the zenith, in Cepheus. I targetted it using the 2.8/180mm Zeiss Sonnar MC lens, snapping pictures during clear spells. It shows up well, as a tiny but clear trail (indicated by the arrow in the image):

click image to enlarge

This object is one which our analysts cannot link to any particular launch - hence the designation "Unknown". It is being tracked by us for quite a couple of years now (since Greg Roberts discovered it on 30 December 2005). It could be either a (defunct) payload, or an old rocket booster.

At the time of my observations it was at an altitude of 36650 km, close to its apogee, situated over the Arctic circle roughly above Iceland:

orbital position of Unknown 051230 at the time of observation
click image to enlarge

Nadir view from orbital position of Unknown 051230 at the time of observation
click image to enlarge

Highly Elliptical Orbits (also called a Molniya orbit) typically have an orbital inclination near 63.4 degrees, an apogee near 36000 km, and perigee at only a few hundred km altitude, usually over Antarctica.

63.4 degree orbital inclination of Unknown 051230
click image to enlarge

The ~63.4 degree inclination with these orbital parameters ensures that the perigee is stable, i.e. always stays over the southern hemisphere.

An object in this orbit has a period of 0.5 day, so it makes 2 revolutions per day. Its residence time in perigee over the southern hemisphere is only brief: most of the time it is at high altitude over the northern hemisphere, allowing many hours of  continued presence above that area (see image above).

Objects in these orbits are therefore typically used to provide communications at high Northern latitudes, or for SIGINT and infra-red surveillance.

Tuesday, 23 September 2014

USA 186, bright and fast

USA 186 (top) and an old Russian r/b (1988-039B, lower corner)
click image to enlarge

Yesterday evening at the end of twilight, I observed USA 186 (2005-045A) pass amidst some scattered clouds. It had cleared just in time.

Close to perigee, the satellite was moving fast. At 70 degrees elevation due East, it became bright (about mag. +1.5), and then briefly flared to mag -1 near 19:06:20 UTC (22 Sep).

A second bright object was moving lower in the sky, and slower. It was an old Russian rocket from the Kosmos 1943 launch in 1988, 1988-039B.

Unfortunately, it later became completely clouded, so I missed this morning's favourable pass of the ISS and Dragon CRS-4, just hours before berthing.

Saturday, 20 September 2014

USA 186 manoeuvered on the 17th

USA 186 being half a minute late one hour after the manoeuvre, 17 Sept 2014, 19:32:02 UT.  Chinese satellite Yaogan 11 also visible  (click image to enlarge)

Ten days after the first post-summer-glareout observations of the KH-11 Keyhole/CRYSTAL optical reconnaissance satellite  USA 186 (2005-042A), it has made another orbital manoeuvre.

In the evening of Wednesday 17 September I was targetting the satellite in a somewhat hazy sky, using the 1.4/85mm lens and a FOV near the tip of the Big Dipper tail.

To my surprise, the satellite was over half a minute late with respect to a 3-day-old element set. This suggested a  manoeuvre. My observations were corroborated by video observations of Leo Barhorst in the Netherlands and visual observations by Pierre Neirinck in France, obtained during the same pass.

The image above shows one of my images. As it turns out, this image was taken perhaps only an hour after the manoeuvre! USA 186 is overtaking Yaogan 11 (2010-047A) in the image (the fainter shorter, upper trail). Yaogan 11 is a Chinese optical reconnaissance satellite.

Observations the following evening by Cees Bassa and me in the Netherlands showed the satellite running even more late by that time: it passed 6m 32s late, low in the west. My camera caught it very close to the image edge. A few hours later, Kevin Fetter in Canada captured it as well.

The Sept 17 and 18 observations suggest that the manoeuvre happened on Sept 17, just before I did my Sept 17 observations (perhaps only an hour before, i.e. less than one revolution!). The current orbital solutions vary a bit between analysts (the post-manoeuvre observational arc is still short), but they agree in that the manoeuvre slightly adjusted the inclination, raised perigee and lowered apogee.

The new orbit is sun-synchronous and close to a 321 x 417 km orbit (it was 265 x 440 km before the manoeuvre), i.e. perigee was raised by about 55 km and apogee lowered by about 23 km. The new orbit is more circular, and starts to conform to the orbit I envisioned in October 2013. I suspect more manoeuvres gently raising perigee and lowering apogee until an approximate 390 x 400 km orbit is reached will occur over the coming half year.

An analysis using COLA suggests the manoeuvre(s) occured on 17 September, either near 17:46 UT or 18:25 UT. Or perhaps (and I favour that) it was a double manoeuvre, performed near both of these moments.

17:46 UT corresponds to passage through the ascending node on the equator, only minutes after passing through perigee. 18:25 UT corresponds to passing through apogee.

A manoeuvre to change inclination is normally done in one of the orbital nodes, or near the poles. A manoeuvre to raise or lower perigee is normally done while the satellite passes through it's apogee, and a manoeuvre to raise or lower apogee is normally done in the perigee. If either one of these (in the current case: the perigee) closely coincides with passage through one of the nodes, this is the ideal moment to change both peri- or apogee, and the inclination in one boost, which spares fuel.

It is very difficult to  adjust the inclination, change the apogee altitude and change the perigee altitude in one manoeuvre.

My favoured scenario is therefore that a first manoeuvre happened near 17:46 UTC in or near the ascending node (and near perigee). This lowered the apogee altitude from 440 to 417 km, and allowed a slight adjustment of the inclination at the same time. Half a revolution later, while passing through apogee near 18:25 UTC, a second manoeuvre was made to raise the perigee altitude from 265 to 321 km.

(click map to enlarge)

Monday, 15 September 2014

Rosetta's landing spot. In 3D. Woah!

image: ESA

Put on your red-cyan glasses and take a look at the image above (high-res here on the ESA website). It is the chosen landing site of Rosetta's Philae lander on comet 67P/Churyumov-Gerasimenko. Woah!

Saturday, 13 September 2014

KH-11 USA 186 has stabilized its orbit

Note 15/09/2014 9:25 UT: corrected inadvertent apogee - perigee mix-up in 4th paragraph
USA 186 passing in early twilight of the evening of Sept 12, 2014
(click image to enlarge)

At the end of May, Northern hemisphere observers lost visibility of KH-11 Keyhole/CRYSTAL USA 186 (2005-042A) when the midsummer nights became too short. The orbital plane of the satellite was still drifting at that time, a process that started after a manoeuvre in mid-November 2013 (see earlier posts on this blog). The big question was, when that drifting would stop. I expected that when the satellite reached its new intended orbital plane it would manoeuvre into a stable sun-synchronous orbit again.

It now has done so, having manoeuvered probably on or near July 1. The orbital plane drift has stopped.

Kevin Fetter in Canada made a chance recovery of the satellite, the first post-summer glare-out sighting, on September 8: he was looking for another object and saw a "unid" in Low Earth Orbit pass through his field of view, that Cees Bassa was quick to identify as USA 186, in a new orbit. Over the next nights several other observers tracked it (including me on Thursday and Friday evening) yielding a first version of the new orbit it is in.

USA 186 passing close to Arcturus (top left) in the evening of Sept 11, 2014
(click image to enlarge)

The satellite has drastically lowered its perigee apogee by almost 500 km, and gently raised its apogee perigee by a few km. It is now in an approximately 265 x 440 km, 96.9 degree inclined orbit. This orbit is sun-synchronous again.

This means that the RAAN drift relative to the other satellites in the KH-11 constellation that had been going on since mid-November 2013, has stopped. It has finally settled at a RAAN distance of about 25 degrees from USA 245 (2013-043A), the primary West plane KH-11.

Comparing the new orbit to the old orbit suggests that the manoeuvre into the new orbit happened on or near July 1st.

In all, the satellite has kept itself pretty much to the expected scenario which I outlined on this blog in several posts in September and October 2013, e.g. here and here. Following the launch of USA 245 (2013-043A) into the primary West plane of the KH-11 constellation in August 2013, I had predicted that:

1) USA 186, at that time the primary West plane satellite, would migrate its orbital plane to the secondary West plane; 
2) USA 129, the extremely aged satellite in the secondary West plane, would be de-orbitted;
3) after a period of drifting, USA 186 would manoeuvre back into a sun-synchronous orbit again, stopping the RAAN drift, when reaching the intended plane location of the secondary West plane;
4) that in that manoeuvre it would drastically lower its apogee from near 1000 km to near 400 km and gently raise its perigee.

This all has basically happened. It differed on details with my predictions, but the bigger picture is pretty much as I anticipated.

What was somewhat unexpected, is that the satellite had its RAAN drift to a much larger distance with respect to the primary West plane (now occupied by USA 245) than I had anticipated. I expected 10, maybe 20 degrees. It turned out to be almost 25 degrees.

The perigee, although indeed raised, is slightly lower than I expected. The massive lowering of the apogee is exactly how I expected it to be however.

The current orbital plane makes it make passes near 8 am and 8 pm local time.

Meanwhile, there are indications that USA 245 (2013-043A) in the primary West plane has manoeuvered. Russell Eberst still observed it in it's last known orbit from Scotland on Sep 7. Then Bjorn Gimmle from Sweden observed an unknown object on Sep 10, that I suspect is USA 245 after a perigee raising orbital manoeuvre conducted between Sep 7 and Sep 10.

[note 14/09/2014: Mike McC identified Bjorn's object as a Russian r/b near decay]
[note 15/09/2014 9:25 UT: corrected inadvertent apogee - perigee mix-up in 4th paragraph]

Thursday, 11 September 2014

[Updated] You Only Die Twice: the confusing end of the Russian Kosmos 2495 Kobalt-M spy satellite mission

Update 15:00 UT, Sep 11: a very brief update confirming the object was artificial is provided at the end of this post

Introduction: a spectacular fireball over the USA on September 2-3

In the evening of September 2 (in local time: early September 3 in UT), 2014, a spectacular event was seen and filmed in the skies over the southwestern States of the USA. A very slow fireball crossed the skies, seen by many casual eyewitnesses in several US States who reported their observations to the American Meteor Society (AMS). It was also captured by a number of all-sky video stations. A very nice compilation of images and what is known and what is still debated, has been made by Spaceflight101 on their website. Below is imagery of the event by Thomas Ashcraft from near Lamy, New Mexico:

video footage  by Thomas Ashcraft, New Mexico, USA

The event happened on September 3, 2014, between 4:31-4:33 UT (the evening of September 2 in local time) and was seen from Colorado, Wyoming and New Mexico. A very slow fireball, with a duration of at least 40 seconds and variable in brightness in what looks like a semi-regular pattern, moved across almost 180 degrees of sky. It penetrated deeply into the atmosphere, leaving a debris cloud at low altitude lingering for 30 minutes, detected by Doppler weather radar.

Lingering debris cloud on Doppler radar after the event (image: Rob Matson)

Initially seen as a meteor event, it was somewhat ignored by the amateur satellite community until brought to their attention a few days later.

Suspicion of a satellite re-entry

The suspicion arose that this was in fact a satellite re-entry, with the prime candidate being Kosmos 2495 (2014-025A), a Russian Kobalt-M/Yantar 4K2M photoreturn spy satellite. This is a satellite that uses analogue film rather than electronic image sensors. The exposed film is returned to earth in three recoverable return capsules, the last of which also returns the camera (for re-use).

In terms of duration, the September 2-3 event is a borderline case: with a duration of at least 40 seconds but possibly a minute or more, both a very slow 11.8 km/s meteoric fireball of asteroidal origin, or the decay of an artificial satellite are possibilities. [but see update at the end of this post: NASA camera data show it was not a meteor but an object entering from Low Earth Orbit, i.e. a satellite]

Timing and path over the sky however closely match predictions for Kosmos 2495. The observed object passed only ~3 minutes earlier than the predicted pass of the satellite, in a very similar trajectory. This actually fits with a decay, as in a lower orbit the object starts to slightly speed ahead of an object in a similar but higher orbit. The slight eastern displacement of the sky track also fits with this: in a few minutes time, the earth rotates under the orbital plane slightly, displacing the sky track westwards.

Predicted Kosmos 2495 sky trajectory for Thomas Ashcraft's site in Lamy, New Mexico. Note remarks in text about slightly eastward displacement of trajectory for a slightly earlier passing object in the same orbital plane, relative to the sky trajectory shown here
(click image to enlarge)

As this satellite should have been in earth shadow at that time of the event and hence not illuminated by the sun, it is immediately clear that if this was Kosmos 2495, it was in the act of re-entering and already producing a plasma envelope (a fireball).

[paragraph slightly rewritten 12:10 UT, Sep 11]
But why? The last known orbital element set for the satellite with epoch 2 Sep 17:12 UT show it at an orbital altitude too high for an imminent natural decay.

JSpOC however issued an "administrative decay" for the satellite early on September 3, an indication that it has been deliberately de-orbited.

Yet it was unlikely that the Russian military intended this satellite to re-enter over the USA  instead of over Russia itself, or over the Pacific.

So, if this was Kosmos 2495, did something go wrong? It initially looked like it.

Then came the confusion

Then came the confusion. On the Seesat-list, Ted Molczan reported having received reports of sightings of a re-entry earlier that same day, near 18:14 UT on September 2, seen over southwest Kazachstan. A number of video's exist of this event and show a glowing object followed at some distance by a cloud of glowing fragments.

footage from Kazachstan

The location of these observations, timing and general direction fits well with an object on a trajectory to Orenburg in Russia, the designated touchdown locality of the Kobalt-M re-entry capsules. Indeed, the timing of the observations (~18:14 UT) matches a pass of Kosmos 2495 over the area, and the trajectory of the latter indeed brings it over Orenburg near that same time.

So if this was the Kosmos 2495 re-entry over southwest Kazachstan and the Kaspian sea, then what was it that re-entered over the USA 10 hours later?

In denial

Next, the Russian military weighed in and flatly denied that anything went wrong with Kosmos 2495, implicitly suggesting that the object decaying over the USA was not their satellite (spoiler: it nevertheless likely were parts of the satellite, see below).

Multiple parts

For a solution of this confusion, we have to look at the construction of a Kobalt-M satellite, and previous Kobalt-M missions. An excellent and detailed description of the Yantar/Kobalt satellites translated from a Russian publication can be found here on Sven Grahns website.

We have to realize that the Kobalt-M satellites are made up of multiple modules:

1) The Equipment Module (AO) that contains the main power and propulsion systems;
2) The Instrument Module (PO) that contains electronic equipment necessary for the control and functioning of the satellite;
3) The camera re-entry vehicle (OSA), containing the camera and the last batch of film. This is a true re-entry vehicle, designed to survive re-entry through the atmosphere for recovery of the camera and film. The target area for these re-entry vehicles is near the Russian town of Orenburg;
4) a 2.5 meter sun shade with additional antennae and sensors on the tip of the OSA, that is presumably jettisoned at re-entry.

The satellite also has two additional small re-entry and landing capsules for the recovery of film mounted on the side of the OSA: these are jettisoned for re-entry at 1/3rd and 2/3rd into the mission, so should no longer have been present on Kosmos 2495 on September 2.

Of importance is that the OSA re-entry module eventually separates from the satellite for re-entry. This potentially leaves satellite parts in orbit after the OSA re-entry, even though it is generally believed that the AO and PO go down with the OSA, with the AO providing the retrofire burn for the de-orbit of the OSA.

Re-entry of the Kosmos 2495 OSA return vehicle observed over Kazachstan towards Orenburg at 18:14 UT, Sep 2

The event seen from Kazachstan was, given the location and timing, most likely the OSA return vehicle with the camera and film re-entering the atmosphere for recovery at Orenburg. The single object in front visible in the videos is likely the returning OSA itself. The cloud of fragments at some distance behind it, might be the jettisoned sun shade disintegrating in the atmosphere. It could also be the AO (propulsion) module, the PO module, or both (it is believed by analysts that the AO (propulsion) module is providing the retrofire boost necessary for the de-orbit of the OSA re-entry vehicle. It is believed that the OSA does not have its own retrofire rocket).

Additional Kosmos 2495 parts surviving until re-entry over the USA at 4:30 UT, Sep 3

How does this fit in with the observations over the USA 10 hours later?

A clue is provided by previous Kobalt-M missions. At the end of five of these (Kosmos 2410, Kosmos 2420, Kosmos 2427, Kosmos 2445 and Kosmos 2462) pieces of debris were detected and catalogued by US tracking facilities that survived for several hours after the OSA re-entry vehicle touched down at Orenburg. In four of the five cases, it concerns two debris pieces (the fifth case, Kosmos 2462, produced three pieces). These debris pieces had the following SSC catalogue numbers and usually Cospar sub-designations C and D, or D and E:

For Kosmos 2410: 28501 and 28502
For Kosmos 2420: 29258 and 29259
For Kosmos 2427: 32048 and 32049
For Kosmos 2445: 33969 and 33970
For Kosmos 2462: 36821, 36822 and 36823
Of interest is that these debris pieces are only detected at the very end of the Kobalt-M mission, around the time of the OSA return vehicle re-entry at Orenburg. They hence seem to have to do with alterations to the satellite in preparation for the OSA separation and re-entry. As it happened on at least five of the missions, it seems a normal element of these missions. In fact it might have happened on all missions, but not all might have been detected: most of the objects above have only one or two element sets released indicating short detection spans. Their lifetimes typically are no more than a few hours to a day, so they can be missed.

From the catalogued orbits of these debris pieces, there are suggestions that the separation of these objects from the original satellite body actually happens a few hours before the OSA re-entry. For Kosmos 2410, this is very clear as the debris pieces were first detected some 16 hours before the OSA re-entry, and while the A-object (presumably containing the OSA) was still being tracked.

The likely re-entry seen from Wyoming, Colorado and New Mexico 10 hours after the OSA re-entry vehicle return over Orenburg, could very well concern similar debris pieces generated by Kosmos 2495. Analogues from another Kobalt-M mission suggests this is a realistic option.

The Kosmos 2445 analogue

Kosmos 2445 (2008-058A), another Kobalt-M mission from 2009, provides a very nice analogue. On its last day of existence it produced two debris pieces with catalogue numbers 33969 and 33970, that survived for several hours after the OSA re-entry. The OSA return occured on 23 Feb 2009 at 16:15 UT. We know this because this OSA re-entry was observed, as reported by Lissov. The last available tracking data for the two Kosmos 2445 debris pieces have an epoch near midnight of Feb 23-24, 2009, indicating survival for at least 8 hours after the Kosmos 2445 OSA return at Orenburg.

I have used Alan Pickup's SatEvo software to further analyse the likely decay time for these debris pieces: the analysis suggests decay near 1:30-1:40 UT on 24 Feb, 2009. This is 9.5 hours after the OSA return.

This 9.5 hours survival time of the Kosmos 2445 debris pieces is similar to the time difference between the Sep 2, 18:14 UT Kosmos 2495 OSA return observed from Kazakhstan, and the possible decay event observed over the USA at Sep 3, 4:30 UT. The time difference between these is about 10 hours, which is not much different from the ~9.5 hours for the Kosmos 2445 debris in 2009.

During their last few orbits in February 2009, the Kosmos 2445 debris pieces C and D moved somewhat in front of where the A-object (the part including the OSA re-entry module) would have been had it not been de-orbitted. The difference in pass time was a few minutes.

Relative position of Kosmos 2445 C and D debris pieces a few minutes in front of where the A-body would have been, just before decay early Feb 24, 2009 (movement is top to bottom)
(click image to enlarge)

This again provides a nice analogue to the September 2-3 event over the USA: the decaying object observed from the USA moved along the Kosmos 2495 A-object trajectory, but passing 2-3 minutes earlier than the predicted A-object passage (i.e., it was moving slightly in front of where the A-object would have been had it not been de-orbitted over Orenburg). Also note the slight westward displacement of the A object (red) trajectory.

So: likely Kosmos 2495 debris re-entering over the USA after all!

I feel that this all justifies to conclude that what was seen from the USA on the evening of September 2-3, indeed were parts of Kosmos 2495 re-entering. The close agreement of the observed fireball track with the predicted trajectory and predicted pass times for Kosmos 2495 is too good to be likely coincidence. The whole event moreover fits patterns of previous Kobalt-M missions, notably that of Kosmos 2445 in 2009: debris pieces surviving for a few hours after the OSA return vehicle re-entry, decaying ~ half a day later.

So while it was not the return capsule with the camera and film that re-entered over the USA, it were nevertheless almost certainly parts of Kosmos 2495.

Remember that denial (see another version here) by the Russian military? Read it carefully. What they actually deny is that Kosmos 2495 exploded, and they say "that nothing out of the ordinary happened".

That is true. The return capsule separated successfully and presumably landed safely at Orenburg near 18:14 UT, as observed from Kazachstan. And Kosmos 2496 did not explode over the USA: debris parts left after the OSA separation decayed over the USA. Generation of such debris pieces seems to be normal for a Kobalt-M mission. So yes, "nothing out of the ordinary happened". It is all a clever word game.

On the nature of those debris pieces

What the nature of those debris pieces generated at the end of most (if not all) Kobalt-M missions and probably seen decaying over the US exactly is remains unclear. Behind the scenes, several independent analysts including me have had e-mail discussions about this the past 24 hours. Separation of the Kosmos into three modules (AO, PO and OSA), one of which (the OSA) makes a controlled re-entry over Orenburg for recovery, would make you think the remaining two debris pieces are these two other modules, the OA and PO. However, it is generally believed that the AO/PO combination provides the retrofire necessary for the OSA de-orbit and hence goes down with the OSA.  It is believed that the OSA module itself has no retrofire capacity (if it would have, it would separate from the other modules and then fire its own retrorocket, leaving the other two modules in orbit).

So analysts have proposed that the debris pieces instead are satellite parts like solar panels (which are 6 meters in lenght each)  and antennae shed somewhat before the OSA re-entry. That idea is more likely yet in itself not entirely unproblematic either. In the case of Kosmos 2410 in 2005, the debris pieces were generated at least 16 hours (if not more) before the OSA reentry. It seems somewhat unlikely that you shed power sources (solar panels) and communication equipment (antennae) so many hours before the OSA re-entry.

The observations from the USA on September 2-3 suggest a seizable object. This is not small debris, but definitely a large object.

So that part of the story remains a bit of a mystery.

UPDATE 1, 11 Sep 2014, 15:00 UT:

Dr Bill Cooke of the Meteoroid Environments Office at NASA's Marshall Space Flight Center informed me (and this information is posted here with his kind permission) that their camera systems catched the event from New Mexico. From the data they determined that the object entered with a speed of  7.69 +/- 0.07 km/s.

That is too slow for an object in heliocentric orbit (a meteor), but the typical speed of an object entering from Low Earth Orbit. Basically, this confirms that the event over the USA was the decay from orbit of (a part of) an artificial satellite.

I thank Dr Cooke for communicating this vital piece of information.

UPDATE 2, 15 Sep 2014, 15:30 UT: 

Ted Molczan has published an excellent analysis into the area-to-mass ratio's of past Kobalt-M debris, which compares favourable to the area-to-mass ratio needed for Kosmos 2465 debris shed at OSA separation to decay over the US at 4:33 UT.

Acknowledgement: I thank Ted Molczan, Jon Mikkel and Jonathan McDowell for the exchange of ideas. Igor Lissov provided valuable data on the Kazakhstan sightings and earlier sightings of Kobalt-M OSA re-entries from that region on Seesat.