Falcon 9 reentry burn from SAOCOM 1A launch observed from Europe

image (c) Koen Miskotte. Used with permission
click image to enlarge

On 8 October 2018 (7 October local time) at 2:21 UT, SpaceX launched the Argentinian Radar surveillance satellite SAOCOM 1A (2018-076A) in a sun-synchronous ~620 km orbit. The launch took place from launch platform 4 at Vandenberg in California. It was a spectacular launch, yielding spectacular launch images.

An hour later, near 03:40 UT, a bright fuzzy blue object travelling through the sky was seen from northern Europe.

This fuzzy phenomena was the Falcon 9 rocket stage (the 2nd stage) form this launch performing its re-entry burn while passing through apogee, lowering perigee such that it would reenter into the atmosphere over the Pacific Ocean southeast of Hawaii near 04:13 UT, at the end of it's first revolution.

The image above is part of an image taken by a photographic all-sky meteor camera in Ermelo, the Netherlands, operated by Koen Miskotte. It is actually a stack of 4 separate images (hence the three short breaks in the trail), of 88 seconds exposure each, taken between 03:39:30 and 03:45:28 UT on Oct 8, 2018. The bright blue fuzzy streak above the treeline is well visible.

The map below shows the trajectory of SAOCOM 1A during the first revolution. It passed over eastern Europe around 03:40 UT (in making this map I used the orbit of the payload as a proxy, as there are no orbital elements of the rocket stage. At this stage of the launch, the rocket stage will have been close to the payload in a similar orbit).

The map also depicts the deorbit area near Hawaii. The deorbit burn initiating the de-orbit happens about half a revolution earlier (some 45 minutes before reentry) in apogee of the orbit, i.e. over Europe:

click map to enlarge

A surveillance camera from a weather station in SüderLügum in Germany, near the German-Danish border, produced this spectacular time-lapse movie of the event (note the "puffs when the rocket engine is firing):




The sky map below shows the trajectory for SAOCOM 1A for Ermelo, the location of Koen Miskotte's alls ky camera (times are in CEST = UT +2). The full all sky image is given as comparison. The two match well:

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image (c) Koen Miskotte. Used with permission
click image to enlarge

Fuel dump of Zuma's Falcon 9 Upper Stage observed by a Dutch pilot over east Africa (and rumours that Zuma failed)

image (c) Peter Horstink, used with permission
click image to enlarge

The spectacular image above was taken by Peter Horstink, the Dutch pilot of a Boeing 747-400 freighter aircraft (Martinair Holland flight MPH8371 from Amsterdam to Johannesburg), around 3:15-3:20 UT on January 8. The aircraft was flying at 35000 feet just north of Khartoum, Sudan, at that moment, which can be seen in the foreground (the yellow lights). The image above is the first one out of four images taken by Horstink.

The spectacular green-blue "spiral" on the image is, given time and location and character, almost certainly the Falcon 9 Upper Stage from the launch of the classified Zuma satellite that day (see my earlier post here), depressurizing and venting fuel at the end of its de-orbit burn. Some 15-25 minutes later, it would re-enter in its designated re-entry zone in the southern Indian Ocean (see map below).

Horstink described his observation as follows (translated from his Dutch e-mail report):

"It started with a greenish light in the top of my front window. At first I thought it was a reflection from some lightsource behind me, but it turned out not to be. At about 218 UTC [this later turned out to be a mistake and must read 3:18 UTC: the aircraft passed Khartoum near 3:25 UTC - ML] with a  very clear sky and with Khartoum in our sight, a point of light (like a star but somewhat bigger) moved from above us to South of us. It moved slower than a usual satellite but clearly did move. I estimate we saw it for 2-3 minutes. The waning moon crescent at that time was almost right above us. The object was surrounded by a greenish glow in the shape of spiral arms, like a spiral galaxy. Two of them, which didn't seem to move much. The total  size of the phenomena was about three times the diameter of the moon."

(note that when measured from the photographs using the star background as a reference, the actual diameter of the spiral cloud is about 11 degrees. The cloud is at ~8 degrees elevation over the horizon, near azimuth 155 degrees. The two bright stars to the right of the cloud are alpha and beta Centauri ).

The map below gives my estimated trajectory for the Falcon 9 Upper Stage, with apogee at ~900 km. It fits the area of the sighting, the launch hazard zone direction and the de-orbit zone position (from Maritime Broadcast Warnings) in the Indian Ocean. The Falcon 9 Upper Stage should have re-entered into the atmosphere between 3:30-3:45 UT, about 30 minutes after the  window from the Maritime Broadcast Warning opened at 3:00 UT.

click map to enlarge

The sighting points to a somewhat higher orbital altitude for Zuma than I had anticipated before the launch: with hindsight, I had too much of an idée-fixe that the orbital altitude would be similar to that of USA 276. The Falcon 9 sighting over East Africa suggests an altitude over double as high, in the order of 900-1000 km rather than my original 400 km estimate.

The sighting does confirm the 50-degree orbital inclination of the orbit. A new estimated elset based on this revision of the orbital altitude is here.

The map below shows the (very) approximate position of the aircraft at the time of Peter Horstink's observation relative to the Falcon 9 trajectory (times in UT, January 8th 2018). The aircraft was flying on a heading of 170 degrees, and Horstink gives his position as "between waypoint Alpox and Khartoum VOR" which corresponds to about 16.38 N, 32.35 E. The Falcon 9 Upper Stage was coming down at an altitude in the range of 200-400 km at that time. Approximate positions for the Falcon 9 Upper Stage are indicated in 2-minute intervals:

click map to enlarge

Horstink made the image above and below plus a few more with a handheld camera, from the cockpit of the aircraft.

image (c) Peter Horstink, used with permission
click image to enlarge

Horstink's observation is not the only observation. Very similar photographs showing a spiral in the sky have been coming from the ground in Sudan, e.g. in this tweet:

Seen at 515 over Sudan. Timeline matches up for Zuma. 🚀🛰🇸🇩 Looks very unnorminal pic.twitter.com/OCDGdyGAZP

— Sam Cornwell (@Samcornwell) 8 januari 2018

image from the ground, from Sudan (author unknown)

On rumours that Zuma failed

The sightings from Sudan near 3:15-3:20 UT are significant, as in the late afternoon of the 8th, rumours appeared on Twitter of a Zuma launch failure. These rumours then were picked up by some news outlets, e.g. here and here.

I have no idea about the veracity of these rumours, and so far SpaceX has said the mission was "nominal" (indicating no problems with the Falcon 9), while Northrop-Grumman and the US military haven't given comments (they never do about classified mission status). They could very well just be rumours, perhaps born out of a misunderstanding of events in the launch seen from the ground by lay observers.

For the moment, unless the US Government comes with some statement, I think it is wise we should treat it as "just rumours", and not necessarily true.

The sighting of the Falcon 9 Upper stage venting 2 hours 15 minutes (1.5 orbit) after launch, bear significantly on the discussion, as it seems to confirm the remarks by SpaceX that the mission was nominal. Of course, for SpaceX the mission ends at orbit insertion.

At any rate, it shows that at least the Upper stage achieved orbit (so it was definitely not a launch failure where the rocket failed to achieve orbit), and it makes sense that the payload then did as well.

So if something went wrong, if at all (a big "if" - I am skeptical), then there are three options left:

(1)  Zuma was inserted into orbit, but it is in the wrong orbit (too high, too low); 

(2)  Zuma was inserted into orbit, but is "dead", i.e. non-responsive;

(3)  Zuma achieved orbit with the Upper Stage, but failed to detach from the Upper Stage, and next de-orbitted with the Upper Stage near 3:30-3:45 UT.

JSpOC ("NORAD") did enter an object from this launch into its master catalogue on January 9th, as object nr. 43098, COSPAR 2018-001A, name USA 280. They designated it "PAYLOAD" (and the USA 280 designation would point to this as well). As usual for classified missions, they do not give details on the orbit.

screenshot showing the JSpOC master catalogue entry for a "PAYLOAD" named USA 280 associated with the launch

This suggests something achieved orbit long enough (i.e. over more than one orbit) to be detected and added to the catalogue.

While this does not necessarily mean the object is still in orbit (and it could in theory reference the Falcon 9 Upper Stage, with the "PAYLOAD" designation then in error), it does fuel my skepticism towards the truth of the rumours.

If Zuma is on-orbit but did fail, the situation becomes reminiscent of the USA 193 saga - an experimental satellite launched in December 2006 that failed after orbit insertion, and a year later was shot out of the sky with an SM3 missile, which has become infamous as "Operation Burnt Frost".

With regard to the observed fuel dump/depressurization: this is normal for most launches and does not necessarily indicate something's wrong.

Rocket stages always carry excess fuel, as you don't want the engine to cut out prematurely by running out of fuel. So it always has a sufficient fuel margin. Once its work is done, this excess fuel is often vented, also known as "depressurization".

[update] An earlier example of such a spiral resulting from a Falcon 9 venting fuel after launch into LEO, is this one from a SpaceX Falcon 9 test launch of a DRAGON in 2010. So this event over Sudan is not unusual. [end of update]

Depressurization and fuel venting avoids the risk of the rocket stage blowing up, for example as a result of static electricity building up in the rocket stage. You do not want your rocket stage to blow up, as it creates an uncontrolable swarm of debris and includes the risk that particles are ejected into orbits where they do not decay quickly,  adding to the space debris risk.

The spiral pattern results when the rocket stage is spinning, perhaps as result of the fuel vent.

At the moment, Zuma is not visible from the Northern hemisphere because all passes are in daylight or earth shadow. This will change 1-2 weeks from now, depending on the exact orbital altitude. The sighting from Sudan does confirm the orbital plane the object should be in (that is: unless it did a manoeuvre into another orbital plane after separation from the Falcon - but I doubt that). So we have to wait now untill a new object is observed in this orbital plane.

The hunt is on!


UPDATE: some news sources are now claiming sources within the US military and US Government confirm the failure, saying the second stage of the Falcon 9 "failed" and stage and satellite crashed into sea.

This does not tally with the observations over Sudan, which show the Upper Stage did reach orbit. So my skepticism remains. If there is some truth to it nevertheless, it could point to option (3) above and subsequent misinterpretation in the press.

UPDATE 2: the adapter mating ZUMA to the Falcon 9 Upper Stage was not made by SpaceX, but by Northrop-Grumman itself (which is somewhat unusual). So if ZUMA did not separate from the Falcon 9 (and did a dive into the Indian Ocean with it), the blame is not on SpaceX but on Northrop-Grumman. In that case, the SpaceX declaration that the Falcon 9 performed "nominal" is correct, even if Zuma did not separate from it.

UPDATE 3 (17 jan 2018): It turns out that a ~52 degree inclined, ~660 km altitude orbit also fits the constraints of the de-orbit area and being over East Africa at the right time. So we are adding that option to the search efforts. I did a partial plane scan of the 50-degree orbital plane two days ago.

click map to enlarge

Ackowledgement: I thank Peter Horstink for his report, for providing additional information on request, and for the permission to feature his images on this blog. I thank Govert Schilling for bringing me into contact with Peter Horstink. The photographs with this post are (c) Peter Horstink.

KH-11 USA 129 is missing, USA 186 has still not manoeuvered

USA 129 (96-072A), the oldest of the KH-11 Keyhole/CRYSTAL/KENNAN optical reconnaisance satellites, has gone missing. The last observers to see it were me on April 22 and Russel Eberst on April 24. The photo below shows one of my images from April 22, with USA 129 passing near Castor and Pollux:

click image to enlarge

Somewhere between that date and May 1, when various observers noted it missing, it disappeared.

There is a possibility that it has been de-orbitted, as it is over 17.5 years old now and appears to be 'redundant' after the launch of USA 245 and plane move of USA 186 (see various earlier posts on this blog). On the other hand, we should be cautious and not too hasty: in the recent past (Feb 2014) we erroneously wrote USA 129's eulogy before, and it turned out it had just manoeuvered. Maybe it did this time as well. A dedicated plane watch I did in the evening of 3 May between 20:41 -21:05 UT yielded nothing.

Meanwhile, we had expected USA 186 (2005-042A) to manoeuvre early May. But up to yesterday May 4th it hasn't. Maybe it will do in the coming days. On May 1st the difference in RAAN with the main West plane KH, USA 245, was 19.8 degrees. At a drift rate of 0.11 degrees/day, it reached 20 degrees the past weekend. If it hasn't manoeuvered by the end of the coming week, it will become interesting. Unfortunately, it is disappearing in evening twilight for my location these days.

The image below shows USA 186 crossing Canis minor in deep evening twilight of May 2nd:

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I imaged USA 245 (2013-043A), the current main West plane KH-11, last Saturday evening. In evening twilight, it was visible in the same camera field with FIA Radar 1 (2010-046A):

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USA 129 does a Mark Twain!

As I wrote in a previous post last week, the KH-11 Keyhole/CRYSTAL optical reconnaisance satellite USA 129 (1996-072A) had not been seen since January 27. We therefore presumed it might have been de-orbitted, as it is very old (17+ years, the longest operational lifettime of any of the KH-11's) and USA 186 is to take over its former orbital plane in two days from now.

We were wrong: USA 129  is still alive!

Greg Roberts observed it from S-Africa last night, after a dedicated 2.5 hour plane scan, and observed it over two passes. A quick fit to his observations by Ted Molczan suggests that the perigee of the satellite might have been brought significantly down, to 240 km (was 310 km). More observations are needed to say anything more about this.

This is something new. I really did not expect USA 129 to manoeuvre into a new orbit.

It should be noted that Ted Molczan already had a hunch about this: as USA 129 was running a bit late when Greg observed it on Jan 27th, Ted felt this could indicate it had made a manoeuver in the hours just prior to Greg's observation. It is now clear he was right: kudos to Ted!

The question now is: what does it mean? Do they have some new purpose for the satellite? At its age of 17+ years, that would be amazing! This is option #1 and perhaps the preferred option. The new orbit appears to be sun-synchronous, which is preferable for an operational optical reconnaissance satellite.

Or is this all in preparation for a de-orbit later (option #2)?

If they are running low on juice for example, they might have opted to bring the perigee of USA 129 down as far as possible and next use natural decay to bring down USA 129 even more, to say 150 km, and then do a final de-orbit burn (option #3). This is a scenario a bit similar to what NASA did with UARS in 2011 (except that they could not do a final de-orbit burn and had it re-enter uncontrolled, something which I don't expect for USA 129). But that is (extremely) wild speculation.

It will be interesting to see what happens with USA 129 the coming days, weeks and months.

Another interesting moment will be reached in two days from now: will USA 129's younger sister ship USA 186 (2005-042A), indeed be boosted into a more circular orbit, as I expect?

[UPDATED] USA 129 de-orbitted [NO!]? And USA 186 about to manoeuvre?

UPDATE 04 Feb 2014: USA 129 was NOT de-orbitted! Greg recovered it on Feb 3. It appears to have manoeuvered into an orbit with a much lower perigee. More here.

USA 129, the oldest orbiting member of the KH-11/CRYSTAL optical reconnaissance satellites, appears to have been de-orbitted during the past week.

(click image to enlarge)

USA 129 on 28 September 2013
RIP ?

On January 27, Greg Roberts in South Africa observed USA 129 (1996-072A) and USA 186 (2005-042A), two of the west plane KH-11 satellites. When he observed again on January 30, USA 129 was gone. He could not spot it on two good passes that evening.

This non-observation raises the serious possibility that USA 129 has been de-orbited somewhere between Jan 28 and Jan 30, 2014. [Update 4 Feb 2014: it was not!]

A de-orbit fits into expectations. In September and October, I published a number of analytical posts on the past and future of the KH-11 KeyHole/CRYSTAL constellation. They detail how I think/thought the constellation of KH-11 satellites will be re-arranged following the lauch of a new satellite, USA 245 (2013-043A, NROL-65), into the primary West plane of the constellation on August 28, 2013. The two most pertinent of these posts are the ones here and here.

So far, my predictions seem to have been quite in line with what consequently actually happened. I suggest that this week will see the closing overture of this spatial spy satellite ballet.

I earlier predicted that after a few months of checkout of the newly launched USA 245, the older USA 186 would be moved from the primary West plane to the secondary West plane, by shifting the RAAN of its orbit 10 degrees more westward. In doing so it would take up the position formerly filled by USA 129 during its extended mission. I also predicted that USA 186 will at some point drastically lower apogee, slightly raise it perigee, and circularize it's orbit. I in addition expected USA 129, which was over 17 years old, to be de-orbitted near the moment those goals were attained.

The latter (the de-orbit of USA 129) seems to have happened in the past few days.

So far USA 186 has also been keeping to the plan. In mid-November 2013 (on or near 12 November), USA 186 made a manoeuvre that changed its inclination by 1 degree (see my post here), causing the satellite to temporarily lose sun-synchronisity and causing it to gradually drift in RAAN from the primary West plane towards the secondary West plane. It is nearly there now. At the current drift-rate (delta 0.12 deg/day relative to the sun-synchronous drift value of the other KH-11 satellites), it will reach the former orbital plane of USA 129 and a 10-degree separation in RAAN from USA 245 (now the sole satellite in the primary West plane) within a week from now, on February 6, 2014.

click image to enlarge

The image above shows how as a result of the Nov 12 manoeuvre, the orbital plane of USA 186 gradually drifted (and as of this writing on Feb 1 still drifts) from the primary West plane to the secondary West plane between November 12, 2013 and February 6, 2014. This is exactly what I predicted to happen back in September and October.

(in the images above, the grey line is the orbit of USA 245, the white that of USA 186, and the red that of USA 129)

The next step is that I expect a large manoeuvre by USA 186 on Thursday February 6th, in which it lowers it's apogee (currently at 975 km) to ~390-400 km, and slightly raises its perigee (currently at 260 km) to ~380-390 km, attaining a much more circular and on average lower orbit with eccentricity close to 0.00055 (currently 0.05) and Mean Motion near 15.59 revolutions/day.

The current orbital inclination of  96.91 degrees is already very close to the 96.99 degree value with which such a 390 x 400 km orbit is sun-synchronous. Lowering apogee and perigee to these values hence would restore a sun-synchronous orbit and stop the drift in RAAN relative to the other satellites in the constellation. As such, the 1 degree inclination change in the satellite's orbit introduced mid-November might be a strong clue that indeed a 390 x 400 km orbit (similar to USA 161, in the secondary East plane) is intended.

click image to enlarge

The image above shows the KH-11/CRYSTAL constellation as of 28 January 2014, and excluding USA 129 which was de-orbitted on or very shortly after that date. The small yellow arrow perpendicular to the orbital plane of USA 186 indicates that I expect it to shift by an extra 0.6 degrees over the coming week.

The image below shows how the constellation will look like after the apogee-perigee changing manoeuvre which I expect USA 186 to make on Feb 6. Note the lower, more circular orbit of the latter compared to the image above:

click image to enlarge

click image to enlarge

As a caveat, there is a very small, alternative possibility that USA 186 will not manoeuvre on Feb 6th. In that case, it will keep drifting another 2.5 months untill the RAAN (orbital plane) difference with USA 245 reaches 20 degrees (and the RAAN separation of the outermost, secondary E and W planes 90 degrees). My hunch is however that this will not happen, and USA 186 will manoeuvre on Feb 6th into a sun-synchronous orbit with RAAN 10 degrees from the RAAN of USA 245, as explained above.

Note: many thanks to Greg Roberts, South Africa, for keeping an eye on the KH-11 satellites during the Northern hemisphere winter blackout!

Past and future of the KH-11 Keyhole/Evolved Enhanced CRYSTAL constellation (part 4)

In a number of previous posts from the last month (this one being the most pertinent one), I probed the changes to the KH-11 Keyhole/CRYSTAL optical reconnaissance satellite constellation over the past 8 years, aiming to predict what will happen now USA 245  has been added to the constellation on 28 August 2013 (launch NROL-65).

The previous analysis was focussed on the orbital planes of the satellites. In this fourth post in this series, I will take a look at other orbital parameters, such as apogee and perigee heights, eccentricity and mean motion.

West plane KeyHole/CRYSTAL satellites:

 USA 129: launched in 1996,
now in secondary West plane, 
probably soon to be de-orbited?

(imaged 28 Sep 2013)

 USA 186: launched in 2005,
soon to switch from primary West plane to 
secondary West plane?

(imaged  5 October 2013)

USA 245: launched 28 August 2013
into the primary West plane

(imaged 5 October 2013)

Let me first briefly summarize the previous analysis. In these I showed that the KH-11 constellation consists of two primary orbital planes separated by 48-50 degrees in RAAN. In addition, each primary orbital plane has an accompanying secondary orbital plane, 10 degrees more west for the West plane and 20 degrees more East for the East plane.

Satellites are initially launched into one of the primary planes, in their primary mission: after a couple of years, and after a replacement has been launched into the same orbital plane, they shift to the accompanying secondary plane, going from primary mission into secondary extended mission.

For example, USA 129 did this in 2006 after the launch of USA 186; and USA 161 did this in 2011 after the launch of USA 224. I pointed out that I expect USA 186 to do the same early 2014 following the recent launch of USA 245 into the West plane. I also expect USA 129 to be de-orbitted.

The graphic summaries given in that previous post, were these two images (see previous post for discussions):

Shifting from primary to secondary orbital planes is however not the only thing that happens. When we look at various orbital parameters, we can see other, accompanying patterns, notably in the apogee and perigee heights:

(click diagrams to enlarge)

(note: all the orbital parameters used in the diagrams above have been determined by Mike McCants from amateur observations, including mine).


New plane, lower apogee altitudes, and more circular orbit

For example: in the previous post on this topic it was discussed how USA 161 (2001-044A) in the East plane manoeuvred from the primary East plane to the secondary East plane late 2011 by changing its RAAN by 20 degrees (i.e., by rotating its line of apsides). This followed the launch of USA 224 (2011-002A) into the primary East plane, as a replacement for USA 161.

In the diagrams above, we can see that other orbital changes took effect as a result of the same series of manoeuvres. In addition to its orbital plane, USA 161 (blue dots in the diagrams) also changed its orbital eccentricity and its apogee and perigee heights. The apogee height was significantly lowered (which initially confused analysts at the time), from about 960 km to eventually about 390 km altitude. The perigee height was raised somewhat, from 310 km to 390 km altitude. The result is a much more circular orbit.

The inclination of the orbit was also changed, by about one degree. The reason for this can be seen in the lowermost diagram: with the changes in apogee and perigee altitudes, the orbital inclination had to be changed to make the resulting orbit sun-synchronous again.

In all, although much of this was accomplished within 6 months after the massive manoeuvre of late August 2011, it took USA 161 about a year to settle in its new orbit.


A repeat of an earlier case

Earlier, in 2006-2007, changes in the orbit of USA 129 (1996-072A) in the West plane can be seen to follow a somewhat similar pattern.

After the launch of USA 186 (2005-042A) into the primary West plane in 2005, USA 129, by that time already 10 years old and hence quite of age, moved to the secondary West plane by changing its RAAN by 10 degrees. Accompanying this move, is a change in perigee and apogee altitudes. The perigee is gently raised from about 280 km to eventually 310 km altitude. The apogee is lowered from about 1020-1030 km to eventually about 770 km altitude. The orbit becomes much more circular as a result.

With USA 129, this process took much longer than with USA 161 and the changes are less drastic. Yet the ideas behind them are clearly similar to what USA 161 did five years later: change orbital plane from primary to secondary plane, lower apogee significantly, raise perigee gently, and circularize the orbit (although not to the degree like USA 161 later did).

The more gentle approach taken by USA 129 in 2006-2007 compared to USA 161 in 2011-2012 might implicate either of these two scenarios:

(a) USA 129 had less fuel reserves left in 2006 than USA 161 had in 2011;

... or (and I prefer this explanation):

(b) it was anticipated in 2006 that the lifetime of  USA 129 needed to be prolonged untill well after the initial lifetime estimates, putting restrictions on fuel use for manoeuvres.

Remember: this is around the time the KH-11/CRYSTAL follow-up program, the FIA Optical program, entered delays and was next cancelled. So option (b) could well be the case.


What to expect?

Based on these past patterns, I expect USA 186 to do the following things by means of  a series of manoeuvres starting the first months of 2014:

1) change RAAN by 10 degrees (i.e. rotating its line of apsides), moving itself from the primary West plane into the secondary West plane (see previous post here);

2) drastically lower apogee (currently at about 1020 km) to about 390 km altitude;

3) gently raise perigee (currently at 260 km) to about 390 km altitude.;

4) circularize its orbit as a result of (2) and (3);

5) change inclination by about one degree to re-attain sun-synchronicity after the altered apogee and perigee altitudes.

These changes should take a few months and be completed towards the end of 2014. They will likely be initiated by a large manoeuvre early 2014 (in February or March likely).

As mentioned earlier I expect USA 129 to be de-orbited this winter or spring.


Why the apogee and perigee changes?

One question pertaining is: why these changes in perigee and notably apogee? Is a circular ~390 x 390 km orbit easier to maintain? Is there instead some operational reason behind this change in altitudes, in terms of desired track-repeat intervals or equipment performance (e.g. demands of image resolution)? If  so, why are similar changes not made to the orbits of the primary plane objects but only to the secondary plane, extended mission objects? I have no answers, and at best I can speculate from a few ideas I have. That is not for this blog, however.


This post benefitted from discussions with Ted Molczan and Cees Bassa. Interpretations and any errors theirin are mine.

Past and future of the KH-11 Keyhole/Evolved Enhanced CRYSTAL constellation (part 3)

In my previous post I outlined in detail how information gleaned from past changes in the KH-11 Keyhole/CRYSTAL optical reconnaissance satellite constellation might yield a blueprint for changes to be expected in the coming months, following the launch of USA 245 (NROL-65, 2013-043A) into the same orbital plane as USA 186 (2005-042A) last August 28.

click image to enlarge

That discussion involved a look at past configurations, especially the relative positions of the orbital planes of the primary and secondary satellites in the constellation. Based on these past configurations, I concluded:

"After these orbital re-arrangements, USA 224 and USA 245 will be the primary satellites in the East resp. West plane. If history is to go by, their orbital planes will likely be separated by about 48 to 50 degrees. The orbital plane of the secondary East plane satellite, USA 161, will probably be 15 to 25 degrees east from that of USA 224. The orbital plane of USA 186, now the secondary satellite in the West plane, will most likely eventually be located 5 to 15 degrees west from that of USA 245."

This weekend I mapped the history of the KH-11 constellation in somewhat more detail than I did for my previous post (where I only looked at 2007, 2011 and 2013). Based on this more detailed analysis, I think I can constrain the distribution of orbital planes even further. The orbital plane of the secondary West plane satellite, a role USA 186 will take early 2014 if I am correct, will be located 10 degrees west of the primary West plane satellite. The orbital plane of the secondary East plane satellite, USA 161, will maintain to be located 20 degrees west east of the primary East plane satellite.

I can say this with some confidence because this seems to have been the intended nominal KH-11 constellation over the full past 8 years.

Since 2005 I keep an archive of the frequently updated classfd.tle orbit files calculated by Mike McCants: they are based on amateur observations that include mine. From my archives I extracted orbital elements for the KH-11 Keyhole/CRYSTAL satellites with an epoch in early July, for each year between 2005 and 2013. Next, since the orbit epochs in question sometimes differ by a few days, I used Scott Campbell's SatFit software to normalize them all to the same epoch, day yy182 (where yy is the year and 182 is the day number), i.e. July 1st of each year.

By normalizing to the same epoch, the RAAN values of the orbits become directly comparable. RAAN stands for Right Ascencion of the Ascending Node, and this value maps the orientation of the orbital plane in space for the epoch in question. More precisely, the RAAN value gives the angle of the orbital plane in earth-centered space, with respect to the direction of the Vernal equinox at the epoch in question.

click diagram to enlarge

The diagram above maps the RAAN values (in degrees) at July 1 for each KH-11 satellite in each year in the period 2005-2013. The diagram below plots the same data, but then expressed as the difference delta (in degrees) between the planes of the primary East and West plane satellites, as well as the delta between the planes of the primary plane satellites and the secondary plane satellites:

click image to enlarge

A clear systematics can be seen to it. The primary East and West plane satellites (always the newest satellite in each plane) are 48 to 50 degrees apart. The secondary West plane satellite is in an orbital plane 10 degrees more westward than the primary West plane satellite. The secondary East plane satellite is in an orbital plane 20 degrees more eastward than the primary East plane satellite.

These are (of course) similar values to what I reported before, but now much more clearly constrained, documented over a larger time span, the diagrams visualizing the intended spatial arrangement very well. An arrangement that has basically been stable over the past 8 years. Changes in the arrangement amount to satellites switching roles (and orbital planes), but the basic orbital planes that make up the constellation remain the same.

The top diagram visualizes how satellites have switched from primary to secondary roles (and from orbital plane) as new satellites are added to the constellation.

For example, we see USA 129 (1996-072A) switch from the primary West plane to the secondary West plane in 2006-2007, following the launch of USA 186 (2005-042A) into the primary West plane. It does so by changing its orbital plane by 10 degrees. And we see USA 161 switch from the primary East plane to the secondary East plane in 2011-2012 (actually late August 2011), following the launch of USA 224 into the primary East plane. It does so by changing its orbital plane by 20 degrees.

A similar switch will no doubt occur early 2014 (see my previous post), when (if I am not wrong) USA 186 switches its orbital plane by 10 degrees from the primary West plane to the secondary West plane, once USA 245 (freshly launched into the primary West plane last August 28) becomes fully operational.

What can also be seen, is how USA 116 (1995-066A) started to drift away from its orbital plane after 2006, and was next de-orbited in 2008. The suggestion is that this satellite had almost ran out of fuel by 2006, as a result of which it was no longer an option to counter the drift by periodic manoeuvres. By 2008 it was drifting too far from the intended constellation, and the last fuel reserves were then used to de-orbit it. The secondary East plane was then left empty until three years later, in 2011, USA 161 (2001-044A) took on the role previously filled by USA 116. This happened after USA 224 (2011-002A) was launched as a replacement into the primary East plane. As of late 2011, the KH-11 constellation can hence be considered complete again (I have pointed out earlier, in my previous post, that the 2008-2011 gap in the secondary East plane was caused by the delay and then cancelling of the FIA optical program).

Note 12 Oct 2013: a follow-up on this post, discussing other orbital parameters than orbital plane, can now be read here.

On USA 245 and USA 129, and the future of the Keyhole constellation: an afterthought to my previous post

In my previous post I discussed how the new KH-11 Keyhole/CRYSTAL USA 245, launched as NROL-65 on August 28,  has been inserted into the same orbital plane as USA 186, a KH-11 launched in 2005. I also discussed the current KH-11 Keyhole/Evolved Enhanced CRYSTAL optical reconnaissance satellite constellation in that post.

Near the end of my post, I wrote:

"With the optical component of the FIA program cancelled, I suspect all of the remaining post-1996 Keyholes to remain operational for many years. For USA 129 though, the end should come one of these days, perhaps once USA 245 has been fully checked out and is put on operational status."

I have since formulated some more thoughts about the likely timetable and likely sequence of events, which are the topic of the current post.


Current and past KH-11 constellations

The KH-11 optical reconnaissance satellites occupy two orbital planes, a West and an East plane. I have already written about this before in my previous post. The image below (made with JSatTrak) gives a graphic depiction of the KH-11 constellation for early September 2013:

 click image to enlarge

With the addition of USA 245 on August 28, the West plane now consists of three satellites:

USA 129  (1996-072A)  operational, but near operational end?
USA 186  (2005-042A)  operational
USA 245  (2013-043A)  new addition being readied for operation

As I wrote before, USA 129 (1996-072A), the oldest KH-11 still on orbit, is now near an incredible 17 years of operational lifetime. With this, it has had by far the longest life-time of any KH-11 so far (see Ted Molczan's KH-11 lifetime data compilation here).

The East plane consists of two satellites:

USA 161  (2001-044A) operational
USA 224  (2011-002A) operational

A previous satellite in the East plane, USA 116 (1995-066A) was de-orbited in November 2008, some 7 years after USA 161 was added to that orbital plane. This was probably done because it had reached the end of its feasible lifetime (for example, because it was running out of fuel, or because vital components started to deteriorate). It had been operational for 13 years when de-orbited.

With the launch of USA 224 on 20 January 2011, slightly over two years later, the East plane was fitted with a second satellite again. This launch probably came so late, because the new FIA Optical program was originally supposed to take over from the CRYSTAL/KH-11 program by 2008. The FIA Optical program was however delayed and then cancelled, and the KH-11/CRYSTAL program reinvigorated.

The cancelling of the FIA Optical program, leaving the KH-11/CRYSTAL program without a follow-up, is why I think that the remaining Keyholes will remain in orbit for several more years, except for the exceptionally aged USA 129. The KH-11 Keyhole/CRYSTAL satellites are currently the only high-resolution optical reconnaissance satellites available to the NRO, apart from time hired on commercial imaging satellites (DigitalGlobe).

If the lifetime of USA 129 is a guide, the remaining operational KH-11 lifetimes will perhaps be up to five more years for USA 161, perhaps up to ten for USA 186, and perhaps up to 15 years or even more for USA 224 and USA 245.


Re-arrangements after the USA 224 launch in 2011

The history of the previous addition to the KH-11 constellation in 2011 might constitute a blueprint of what will happen the coming months, now USA 245 has been added to the constellation.

In 2011, USA 224 was initially launched into the same orbital plane as USA 161, similar to how USA 245 has now been launched into the same orbital plane as USA 186. A few months after the USA 224 launch the older East plane satellite (USA 161) manoeuvered to a lower orbit (or more accurately: a more circular orbit with lower apogee), on 24 August 2011. This was preceded by a number of smaller preparatory manoeuvres in the previous two months according to Ted Molczan (priv. com.).

This could indicate that USA 224 became fully operational about 5 to 7 months after launch. At that moment it became the primary satellite in the East plane, with USA 161 next taking on a new secondary role in an extended mission, as indicated by its manoeuvre into a different orbit.

Subsequently, the orbital plane of USA 161 was allowed to drift slightly eastward. As a result, the orbital plane of the older USA 161 in the East plane is currently located 20 degrees east of that of the newer USA 224,  in a similar vein as the orbital plane of the older USA 129 in the West plane is located somewhat westward of that of the newer USA 186.

(note: the saga of the significant August 2011 manoeuvre of USA 161 and its eventual recovery by observers including me, has been covered on this blog here, here and here).


Current and past plane separations

The orbital planes of the current main West plane satellite, USA 186, and the main East plane satellite, USA 224, are some 48 degrees apart. Likewise, before USA 224 took over from USA 161 mid-2011, the orbital planes of the then main West and East plane satellites USA 161 and USA 186 were 49 degrees apart. Mid 2007, the then main East and West plain satellites USA 161 and USA 186 were 50 degrees apart. This is all very similar, differing by only 1-2 degrees.

click image to enlarge

The orbital plane of the secondary West plane satellite, USA 129, is currently located 10 degrees west of the plane of the primary West plane satellite USA 186. The orbital plane of USA 161, the secondary satellite in the East plane, is located 20 degrees east of the orbital plane of the primary East plane satellite USA 224. Mid 2011 this was 2 resp. 12 degrees, and mid 2007 it was 5 resp. 26 degrees.

In table form, for the current constellation (September 2013):

Epoch 13250   
7 Sept 2013
 
----------------------------------------- 
satellite  RAAN    PER   APO   incl   
(name)     (deg)   (km) (km)   (deg)
-----------------------------------------

WEST PLANE

USA 129    303     308   770  97.56   S 
USA 186    313     262  1017  97.94   P
USA 245    314     262  1010  97.87   fP

EAST PLANE
   
USA 224    01      258  1023  97.88   P
USA 161    21      385   393  97.03   S
-----------------------------------------

P  = Primary
fP = future Primary
S  = Secondary


(In this table, RAAN stands for Right Ascension of the Ascending Node. This value determines the position of the orbital plane in earth-centered space with reference to the vernal equinox point at the epoch in question. PER and APO refer to the altitude of Perigeum and Apogeum, and incl is the orbital inclination. See also here. All data are based on orbital elements calculated by Mike McCants from amateur observations, including mine).

I do not know what the reason is for the asymmetry between the secondary East and West planes with relation to their primary planes (10 resp. 20 degrees currently), although I suspect it has to do with  solar angles at the imaged target locations (the West plane satellites pass in the morning, the East plane satellites somewhat after noon).


Future re-arrangements and expected USA 129 de-orbit

If the pattern after the addition of USA 224 in 2011 repeats in the West plane with USA 186 and the newly added USA 245, I expect USA 245 to become fully operational around February 2014. Around that time it will become the primary satellite in the West plane. Between  now and then, it will probably make more manoeuvers to finalize its intended orbit.

We can then next also expect USA 186 to attain a new secondary role and go into a new extended mission, by manoeuvering into a more circular orbit with lower perigee apogee somewhere in February or March 2014. Next, the orbital plane of USA 186 will probably be allowed to drift somewhat westward, as a result of which USA 186 will take up an orbital plane slightly west of that of USA 245.

Near that same time, and possibly somewhat earlier if time is really running out on it, we might see the de-orbit of USA 129.

After these orbital re-arrangements, USA 224 and USA 245 will be the primary satellites in the East resp. West plane. If history is to go by, their orbital planes will likely be separated by about 48 to 50 degrees. The orbital plane of the secondary East plane satellite, USA 161, will probably be 15 to 25 degrees east from that of USA 224. The orbital plane of USA 186, now the secondary satellite in the West plane, will most likely eventually be located 5 to 15 degrees west from that of USA 245. The  orbital planes of the outer (secondary) East plane and outer (secondary) West plane satellites, USA 161 and USA 186, will probably be separated by about 80 degrees.

(note added 15 Sept 2013: after a more comprehensive analyses of the orbital planes over 2005-2013, I believe the orbital plane of the secondary satellite in the West plane to be placed 10 degrees west of the primary West plane: and the orbital plane of the secondary satellite in the East plane to be placed 20 degrees East of the primary East plane. See my follow-up post here)

Of course, these are all just no more than educated guesses, based on past configurations and re-arrangements of the Keyhole/CRYSTAL constellation. Time will tell us whether this scenario will indeed play out as I outlined above. It is always possible that we will eventually see something completely different!


Sun-synchronous, repeating ground tracks

KH-11 Keyhole/CRYSTAL satellites move in sun-synchronous orbits that have their ground tracks more or less repeat after an integer number of days (1, 2, 4 or more days). The goal is to obtain comparative images of the same location taken a few days apart, taken with similar illumination by the sun (i.e., similar shadows). This aids the analysis of the images for the detection of any changes on sites of interest.

As I wrote in my previous post, the West plane Keyhole/CRYSTAL satellites make evening and morning passes. The East plane Keyhole/CRYSTAL satellites make passes 1-2 hours after local noon and midnight.

USA 186 and USA 224, the current primary satellites in the West resp. East plane, repeat their ground tracks after 4 days (the 4:59 resonance). USA 129 and USA 161, the secondary satellites in the respective planes, repeat ground tracks after 12 resp. 7 days.

When USA 245 has taken over from USA 186 in the West plane by February-March 2014, we can expect it to have a 4-day ground track repeat interval. It will be interesting to see whether USA 186 will attain a 7-day ground track repeat interval similar to the current repeat interval of USA 161.

(Update added 15 september 2013: A further and well-illustrated update, documenting and constraining the constellation of orbital planes in past and present even further, can be read here).

(Note: I am indebted to Ted Molczan for comments on a draft of this post, and for providing me a spreadsheet to calculate the ground track repeat intervals. Any errors of fact or interpretation in this post are solely mine)

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).

USA 161: "The reports of my death are greatly exaggerated..."

KH-12 Keyhole USA 161 (01-044A) is alive! Pierre Neirinck and I observed it last night around 23:55 UTC (1 Sept). Below is one of the two images of it which I captured:

click image to enlarge

The Keyhole, launched from Vandenbergh on 5 October 2001, went AWOL on or short after 24 August, with several observers failing to observe it in a window well around its last orbital position after that date. This lead to some suggestions, covered earlier here, that it could have been de-orbitted. After all, a new Keyhole, USA 224 (11-002A) had been launched in the same orbital plane on January 20, 2011, ostensibly as a replacement for USA 161.

Not everybody took to the idea of a de-orbit for USA 161 though. It's much older sister ship in the evening plane, USA 129 (96-072A), was after all still active even though USA 186 (05-042A) had been placed in the same orbital plane in 2005. So why de-orbit the newer USA 161 but leave the much older (and presumably less modern) USA 129 up?

The alternative to a de-orbit, was a massive reboost into a different orbit. This option got more credibility when an anonymous radio observer reported the possible reception of a radiosignal from USA 161 on August 26. Based on this possible reception, Ted Molczan dispatched a number of search orbits to the active observers, and the hunt for Red October USA 161 was on...

Skies were overcast in Leiden at that time, but on 28-29 August it cleared somewhat (with the emphasis on "somewhat"). I tried to cover the nominal plane of the search orbits that night (which meant staying up late to 2 am local time) under conditions that can only be described as abominable (thin and sometimes thicker clouds) but failed to recover the satellite. That could easily have been due to the conditions though. In France, Pierre Neirinck suffered the same conditions.

On the night of 30-31 August, Pierre Neirinck in France spotted an object that could be USA 161 near 00:17 UTC. As his sky suffered from clouds, there was some uncertainty in the position he obtained. His observation suggested that the satellite was moving in an orbital plane that was shifted slightly more eastwards than the plane of the search orbits.

On the night of August 31-September 1, Björn Gimmle in Norway possibly observed it again near 23:20 UTC, but he wasn't too sure. Pierre Neirinck observing from France between 22:58-23:23 UTC did not see it. Neither did I, keeping (under good sky conditions) a visual and photographic watch between 23:31-23:46 UTC. Red October USA 161 turned out to be elusive and not willing to give up it's location easily!

Third time is a charm however (or, as we say in Dutch: Drie maal is Scheepsrecht, which is ambiguous to translate beacuse the exact meaning of "scheepsrecht" is under dispute: but it is something like "Three times is Ship's Justice" or "Three times is Alderman's Justice").

On the night of September 1-2, both Pierre in France and I in the Netherlands observed it unequivocally around 23:55 UTC. Keeping a visual and photographic watch under good conditions, I picked it up visually somewhat east of Polaris and under Cassiopeia, and just under the FOV of my camera. I quickly re-aimed and shot two images (one of them shown above), yielding four points. It was steady and at its brightest about mag. +2, a naked eye object. At the same time, Pierre in France also saw it visually and got three points.

With these data of last night, the new orbit is starting to get a bit of shape - probably enough for others to recover it more easily the coming nights. Probably not here at Leiden though: the sky has grown very hazy today (thin clouds) and I need some sleep.

The very preliminary orbit still needs more observations before it becomes accurate, but it looks like the perigee has been significantly raised to twice the altitude it was (from 303 km to ~590 km), and apogee slightly lowered (from 911 km to ~780 km).

These kind of situations, where a satellite makes a big manoeuvre and the hunt is on to recover it, are always exciting times where the hobby gets most fun!

KH-12 USA 161 de-orbited? [updated 02/09/2011]

UPDATE 2 Sept 2011: USA 161 is Still Alive! It has not been deorbitted but made a large manoeuvre. Read more about the recovery here.

Negative observations on Wednesday and Thursday 24-25 and 25-26 August reported by Russell Eberst from Scotland on SeeSat-L and Pierre Neirinck from France (priv. com) suggest that the KH-12 Keyhole USA 161 (2001-044A), an advanced high resolution optical reconnaisance satellite launched on 5 October 2001, has either undergone a large manoeuvre or (more likely) has been de-orbited last week.

Earlier this year (January 20, 2011), USA 224 (2011-002A) was launched as NROL-49 and put in the same orbital plane as USA 161, probably as a replacement for the latter.

Below are two archive pictures I shot of USA 161 brightly flaring twice on 30 July 2009:

click image to enlarge

The remaining KH-12 constellation (if indeed USA 161 has been de-orbitted last week) now consists of three satellites: USA 129 (96-072A), USA 186 (05-042A) and USA 224 (2011-002A), the oldest of which (USA 129) is now 15 years in service.

USA 224 which replaced USA 161 represents the noon and midnight plane. USA 129 and USA 186 represent the morning and evening plane. Below diagram shows the satellite constellation as it is now USA 161 has presumably been de-orbitted:

click diagram to enlarge

Lacrosse 2 is no more.....

A number of non-detections over the past week have confirmed that the classified US SAR satellite Lacrosse 2 (91-017A), the oldest of the still orbiting Lacrosses, has been de-orbited on or around March 26th.

The first to note Lacrosse 2 absent was Russell Eberst in Edinburgh on March 30th - incidently, the very person who also saw it first in March 1991.

This prompted a watch by other observers, including me, who all confirmed the "no-show" of Lacrosse 2.

In the evening of April 1st, I conducted a photographic watch between 19:44:00 and 19:53:00 UTC, keeping continuous coverage of a 18 x 24 degree FOV centered on the nominal position predicted for the satellite for 19:47:30 UTC. Nothing was recorded (another Lacrosse, Lacrosse 4 (00-047A) was recorded in the images when it passed through the same area at about 19:46 UTC).

As it now transpires, probably the last person to see Lacrosse 2 alive was Pierre Neirinck in France at March 25th, 20:19 UTC. Another observer failed to see it on March 26th: quite likely, it was de-orbited only a few hours and orbits after Pierre's observation.

Launched on March 8th, 1991, Lacrosse 2 has been operational for almost exactly 20 years: a long period of active service indeed.

Below are a number of archive images of Lacrosse 2 taken by me in 2008 and 2010. Goodbye, Lacrosse 2, you always were such a nice bright satellite to track.....

click images to enlarge