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#300 by Targeteer on 10 Dec, 2013 01:11
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Numerous amateur observations indicate the payload is in the now standard, expected operational 252 km X 996 km orbit inclined 97.8829 degrees
http://www.satobs.org/seesat/Aug-2013/0210.html
Observers have detected the first maneuver to a 254 X 1002 km orbit
http://www.satobs.org/seesat/Aug-2013/0244.html
Maneuver #2 detected and the orbit is now 265 X 1002 km
http://www.satobs.org/seesat/Sep-2013/0013.html
Correction to the orbit after maneuver #2--259 X 1007 km
http://www.satobs.org/seesat/Sep-2013/0052.html
http://www.satobs.org/seesat/Dec-2013/0061.html
Orbit updated after recovery of USA-245 and -129 by observers.
USA 129 307 X 749 km
1 24680U 96072A 13342.76255084 .00015082 00000-0 24218-3 0 03
2 24680 97.5547 33.8311 0320001 354.8452 4.9507 15.11744450 02
Arc 20131204.85-1208.82 WRMS resid 0.008 totl 0.007 xtrk
USA 245 271 X 982 km
1 39232U 13043A 13342.83426663 .00028645 00000-0 33250-3 0 05
2 39232 97.8249 44.7022 0507521 220.0704 136.2029 14.79901441 07
Arc 20131206.87-1208.89 WRMS resid 0.013 totl 0.007 xtrk
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#301 by Targeteer on 19 Dec, 2013 17:39
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The predicted realignment of the US imagery fleet may have started following the launch/check-out of USA-245.
http://www.satobs.org/seesat/Dec-2013/0138.html
Greg Roberts has recovered USA 186, last seen on day 13269, which he has observed on three passes over two consecutive evenings, yielding the following orbit:
USA 186 258 X 985 km
1 28888U 05042A 13352.82237648 .00025984 00000-0 23965-3 0 08
2 28888 96.9335 49.8482 0519414 203.7413 153.9046 14.81498880 09
Arc 20131217.87-1218.88 WRMS resid 0.014 totl 0.006 xtrk
This orbit reveals a manoeuvre to reduce the inclination, which may have occurred early on Nov 12 UTC. The exact date/time are uncertain due to the along-track position uncertainty over the time span involved. Since RAAN was unaffected, the manoeuvre must have occurred at a node. Indeed, the pre and post-manoeuvre orbits were closest at the nodes. The descending node was not far from apogee, so probably was favoured, due to the somewhat lower delta-V requirement.
The immediate effect of reducing the inclination has been to precess the orbit westward, out of the primary western KeyHole plane, now solely occupied by the recently launched USA 245. The quasi-97 deg orbit may be a clue that it is intended to eventually manoeuvre the spacecraft into a low, circular orbit like that of USA 161 (shown below).
USA 161 389 X 397 km
1 26934U 01044A 13220.08411940 .00013500 00000-0 17063-3 0 00
2 26934 97.0335 351.2744 0005500 40.7551 319.2448 15.59514737 09
Marco Langbroek recently shared his research and ideas on the KH orbits, in which he forecast the westward plane shift
and ~390 km, ~97 deg orbit:
http://sattrackcam.blogspot.nl/2013/10/past-and-future-of-kh-11-keyholeevolved.html
I like Marco's forecast. It will be interesting to see what actually happens.
Greg also made new observations of USA 245, which he recovered earlier this month:
USA 245 257 X 992 km
1 39232U 13043A 13352.83949499 .00033406 00000-0 30426-3 0 06
2 39232 97.8549 54.5218 0524761 187.5843 171.7207 14.80557970 00
Arc 20131208.83-1218.9 WRMS resid 0.014 totl 0.005 xtrk
The larger arc reveals that the perigee height was unaffected by the reboost manoeuvre that pre-dated the recovery. My earlier results indicated an ~14 km perigee-raising, which now seems unlikely.
Ted Molczan -
#302 by Star One on 19 Dec, 2013 18:49
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Why put USA 161 in such a low orbit as being the oldest one in the fleet would it not have less propellant onboard yet be in a orbit that needed more station keeping to preserve it being deeper into the Earth's atmosphere?
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#303 by Targeteer on 19 Dec, 2013 19:20
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Why put USA 161 in such a low orbit as being the oldest one in the fleet would it not have less propellant onboard yet be in a orbit that needed more station keeping to preserve it being deeper into the Earth's atmosphere?
High(er) resolution imagery throughout the orbit would seem the obvious answer. While there would be higher drag consistently through the orbit, there would be less than occurs at the low point of the traditional orbit. I'll leave to the experts to comment on the trade-off of the numbers of re-boosts of the higher/lower elliptical orbit versus the mid-range circular orbit.
Also, USA-161 isn't the oldest member of the fleet, USA-129 is. An interesting discussion would involve why it wasn't moved into the lower circular orbit first... -
#304 by Targeteer on 23 Dec, 2013 18:58
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Marco Langbroek has updated his assessment of the Keyhole constellation realignment based on the USA-186 inclination change.
http://sattrackcam.blogspot.nl/2013/12/usa-186-keyhole-kh-11advanced-crystal.html
"As a result of the inclination change the orbit is no longer sun-synchronous and hence its rate of precession changed. As a result its RAAN is currently shifting westwards relative to the other KH-11's. On December 17 the RAAN of USA 186 had already shifted westwards by 4 degrees. I suspect it will keep precessing until it reaches a value 10 degrees west of what it initially was (see my earlier predictions here, where I predicted this shift in RAAN), close to the aged West plane secondary satellite USA 129 (1996-072A). This shift will have been accomplished by early February at the current rate of precession (0.868 degrees/day or -0.12 degrees/day relative to the sun. Taking into account the RAAN precession of USA 245, they will have a separation of 10 degrees in RAAN by February 5)."
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#305 by William Graham on 23 Dec, 2013 23:35
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Also, USA-161 isn't the oldest member of the fleet, USA-129 is. An interesting discussion would involve why it wasn't moved into the lower circular orbit first...
Having been in orbit longer, 129 will probably have less propellant left than 161 - maybe it has an insufficient amount to be operable in the lower orbit for any meaningful amount of time. It is also worth noting that 161 and 186 could well have been launched with more propellant than 129. USA-129 was the last KH-11 to launch on the Titan IVA, perhaps the extra capacity the Titan IVB offered was used to accommodate more fuel on later spacecraft - maybe even with an extended mission such as this in mind. -
#306 by Star One on 26 Dec, 2013 22:27
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Also, USA-161 isn't the oldest member of the fleet, USA-129 is. An interesting discussion would involve why it wasn't moved into the lower circular orbit first...
Having been in orbit longer, 129 will probably have less propellant left than 161 - maybe it has an insufficient amount to be operable in the lower orbit for any meaningful amount of time. It is also worth noting that 161 and 186 could well have been launched with more propellant than 129. USA-129 was the last KH-11 to launch on the Titan IVA, perhaps the extra capacity the Titan IVB offered was used to accommodate more fuel on later spacecraft - maybe even with an extended mission such as this in mind.
Be interesting to see when 129 gets de-orbited, I expect fairly soon after 161 is in place so sometime in March or April. -
#307 by Targeteer on 06 Feb, 2014 03:17
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Also, USA-161 isn't the oldest member of the fleet, USA-129 is. An interesting discussion would involve why it wasn't moved into the lower circular orbit first...
Having been in orbit longer, 129 will probably have less propellant left than 161 - maybe it has an insufficient amount to be operable in the lower orbit for any meaningful amount of time. It is also worth noting that 161 and 186 could well have been launched with more propellant than 129. USA-129 was the last KH-11 to launch on the Titan IVA, perhaps the extra capacity the Titan IVB offered was used to accommodate more fuel on later spacecraft - maybe even with an extended mission such as this in mind.
Be interesting to see when 129 gets de-orbited, I expect fairly soon after 161 is in place so sometime in March or April.
It's still living after an odd maneuver...
http://sattrackcam.blogspot.nl/2014/02/usa-129-does-mark-twain.html
http://sattrackcam.blogspot.nl/2014/02/usa-129-de-orbitted-and-usa-186-about.html
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#308 by Star One on 06 Feb, 2014 13:08
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Also, USA-161 isn't the oldest member of the fleet, USA-129 is. An interesting discussion would involve why it wasn't moved into the lower circular orbit first...
Having been in orbit longer, 129 will probably have less propellant left than 161 - maybe it has an insufficient amount to be operable in the lower orbit for any meaningful amount of time. It is also worth noting that 161 and 186 could well have been launched with more propellant than 129. USA-129 was the last KH-11 to launch on the Titan IVA, perhaps the extra capacity the Titan IVB offered was used to accommodate more fuel on later spacecraft - maybe even with an extended mission such as this in mind.
Be interesting to see when 129 gets de-orbited, I expect fairly soon after 161 is in place so sometime in March or April.
It's still living after an odd maneuver...
http://sattrackcam.blogspot.nl/2014/02/usa-129-does-mark-twain.html
http://sattrackcam.blogspot.nl/2014/02/usa-129-de-orbitted-and-usa-186-about.html
Thanks for those links. Isn't it a bit unusual to put it on such a low orbit if no other reason that it will make it more easily observable by those on the ground? -
#309 by Jim on 06 Feb, 2014 13:27
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visibility from the ground isn't a consideration nor does the difference really improve visibility from the ground.
edited for clarity -
#310 by kevin-rf on 06 Feb, 2014 14:00
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Lower orbit leads to better ground resolution, so it does have an advantage. So if they are not getting ready for a swan song, what do they need a "better" look at?
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#311 by Targeteer on 16 Mar, 2014 04:34
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Northern hemisphere observers have regained visibility of the western satellite plane and USA-186 has not settled into it's lower, sun-synchronous orbit and continues to drift west.. http://sattrackcam.blogspot.com/
"Now USA 186 has not manoeuvered, it is time to entertain my alternative scenario which I presented near the end of this post on Dec 22 and this post on Feb 1.
That alternative scenario is that the drift will continue until the difference in RAAN between USA 186 and USA 245 amounts to 20 degrees (instead of 10 degrees). This is a RAAN difference similar to that between the primary and secondary East plane satellites, USA 224 and USA 161. It would create a 90-degree angle in RAAN between the outermost, secondary East and West plane satellites (USA 161 and USA 186).
At the current drift rate, these values will be reached early May.
It is clear that the current, drifting orbit of USA 186 is not an intended end state. The orbit is not sun-synchronous, a must for an optical reconnaissance satellite. The inclination change it made mid-November 2013 is such that a manoeuvre into a ~380 x 400 km orbit similar to USA 161 in the secondary East plane will restore a sun-synchronous precession rate. So that appears to be the intended goal in the future. The current non sun-synchronous orbit is meant to let the RAAN drift up to a desired value. The question now is, what final RAAN value relative to the primary plane is intended.
My guess, now it has turned out to be not 10 degrees, is 20 degrees.
Meanwhile, another question is what they intend to do with the "old" secondary West plane satellite, USA 129."
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#312 by Star One on 29 Mar, 2014 18:26
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Quote
In several previous posts from September 2013 onwards, I analysed and prognosed changes to the KH-11 Keyhole/KENNAN/CRYSTAL optical reconnaissance satellite system. Main focus was on the changes, notably in the orbit of USA 186 (2005-042A), following the addition of USA 245 (2013-043A) as a replacement for USA 186 in the Keyhole primary West plane.
Indeed, as predicted, USA 186 was moved out of the primary West plane, and started to drift towards the secondary West plane in mid-November 2013 following a manoeuvre that changed its inclination and made it loose sun-synchronisity.
USA 186 is still drifting westwards. It currently is moving westward at a rate of 0.11 degree/day relative to USA 245 (2013-043A), the primary satellite in the West plane since the autumn of 2013. The difference in RAAN between the two satellites currently is slightly over 16 degrees:
Late 2013 and early 2014, I expected that the drift would end early February 2014, when the RAAN difference between USA 245 and USA 186 reached 10 degrees, the old separation between USA 186 and USA 129, the former primary and secondary West plane satellites. I was proven wrong with my prediction, when USA 186 continued to drift past that date.
I then turned to a second scenario: that the intended RAAN difference between USA 245 and USA 186 will be 20 degrees, similar to the difference between USA 224 and USA 161 in the East plane.
With the current rate of precession of 0.1111 degrees/day relative to USA 245, the RAAN difference between USA 186 and USA 245 will reach 20 degrees near May 1. So I expect USA 186 to manoeuvre into a lower, sun-synchronous orbit on or near that date. The KH-11 constellation will then look like this:
An open question is what will happen to USA 129 (1996-072A), the over 17 year old former secondary West plane satellite. I still think it will be de-orbited somewhere this year. But I have been wrong before.
Note: the orbits for USA 129, USA 186 and USA 245 in the West plane in the images above are based on recent observations. The East plane satellites USA 161 and USA 224 have not been observed since autumn 2013, and will not be visible from the Northern hemisphere before mid-April. There is therefore a possibility that one or both have moved, but since we have no information on their current whereabouts, I have depicted them in their 'old' orbital planes of the autumn of 2013 relative to the West plane.
http://sattrackcam.blogspot.nl -
#313 by Targeteer on 04 May, 2014 03:36
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USA-186 has not maneuvered into a sun-synchronous orbit and -129 was not seen by two leading observers
http://www.satobs.org/seesat/May-2014/0016.html
The evening KH-11's start to disappear in evening twilight for me. 05-042A was
captured in bright twilight using the 85mm lens and short exposures (2.5 s).
Obviously it has not manoeuvered (yet) and is still drifting westwards relative
to the main West KH plane. The RAAN difference with USA 245, the main West plane
KH, is now 20 degrees, similar to what the difference between the main and
secondary East plane satellites (USA 224 and USA 161) was before the winter
blackout. If it does not manoeuvre soon and keeps drifting in a non sun-sync
orbit as it does now, I have no idea what the plan is, if there is a plan.
http://www.satobs.org/seesat/May-2014/0023.html
Marco Langbroek via Seesat-l schreef op 3-5-2014 23:58:
> C. Bassa via Seesat-l schreef op 2-5-2014 22:06:
>> Just a quick heads up that USA 129 was not seen at 19:52UT just now on
>> a favorable pass.
>>
>> Cees
>
>
> Indeed, nothing seen during a dedicated photographic coverage between May 3,
> 20:41:00 - 21:05:30 UT (nominal pass time would have been 22:53:00).
Ummm: 20:53 for the nominal pass-time of course... -
#314 by Targeteer on 09 Sep, 2014 00:22
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USA 186 has apparently been recovered by the amateur astronomers in a 266 x 441 km, 96.9° orbit (updated search TLE on Heavens Above.com) I had a 15 degree elevation pass but the very bright harvest moon and low angle made seeing anything almost impossible
http://www.satobs.org/seesat/Sep-2014/0064.html
C. Bassa via Seesat-l schreef op 8-9-2014 20:53:
> Fitting an orbit to both Kevin and these observations gives:
> 1 28888U 05042A 14251.77652340 .00000000 00000-0 50000-4 0 04
> 2 28888 96.9174 289.4726 0129943 0.3928 51.8245 15.71831976 03
> # 20140908.01-20140908.78, 26 measurements, 0.014 deg rms
When combined with the last known orbit, this actually suggests a manoeuvre on
or near 2014 July 1st ~1:40 UT (but take that accuracy with a grain of salt)
when perigee was over the south pole. Apogee was lowered by almost 500 km.
> Alberto Rango last saw it in June when it appeared to have manouvred
> after having spent a few months in some sort of transfer orbit that
> was precessing its plane West
Alberto actually reported that he failed to see it early June (see his post of
June 9th: http://www.satobs.org/seesat/Jun-2014/0069.html): but during low
twilight passes, which might perhaps explain the non-observations.
Mike McC and another US observer positively observed it late May. So did it
manoeuvre early June, or did we simply lose it in twilight of the N-hemisphere
summer, after which it manoeuvered at July 1st?
Let's see however what results when the current orbit has been better
established with a longer arc.
If USA 245 is still in it's last known plane, the RAAN difference between the
two should now be about 25 degrees.
- Marco
-----
Dr Marco Langbroek - SatTrackCam Leiden, the Netherlands.
e-mail: sattrackcam_at_langbroek.org
Cospar 4353 (Leiden): 52.15412 N, 4.49081 E (WGS84), +0 m ASL
Cospar 4354 (De Wilck): 52.11685 N, 4.56016 E (WGS84), -2 m ASL
Cospar 4355 (Cronesteyn): 52.13878 N, 4.49937 E (WGS84), -2 m ASL
Station (b)log: http://sattrackcam.blogspot.com
Twitter: @Marco_Langbroek
PGP key: http://tinyurl.com/kur7xm8
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#315 by gosnold on 11 Sep, 2014 20:11
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What is the expected lifetime in such an orbit?
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#316 by Prober on 11 Sep, 2014 21:04
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What is the expected lifetime in such an orbit?
Long enough for the mission
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#317 by Targeteer on 14 Sep, 2014 18:12
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http://sattrackcam.blogspot.nl/2014/09/kh-11-usa-186-has-stabilized-its-orbit.html
"Saturday, September 13, 2014
KH-11 USA 186 has stabilized its orbit, USA 245 has manoeuvered?
USA 186 passing in early twilight of the evening of Sept 12, 2014
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
The satellite has drastically lowered its perigee by almost 500 km, and gently raised its apogee 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 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."
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#318 by Star One on 14 Sep, 2014 18:18
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@Targeteer I posted this in the general KH-11 thread yesterday, it just seemed more appropriate in there as it's talking in general about the constellation?
