Tuesday 6 June 2017

[UPDATED] Close Encounters of the Classified Kind: a post-event analysis of the close approach of USA 276 to the ISS on June 3

3 July 2017: A paper which is a further evolved version of this blog post has appeared in The Space Review. I advise you to read that paper

(UPDATED 7 Jun 2017 15:50 UT with two new figures showing circular motion of USA 276 around the ISS)

Something odd happened a few days ago, high above our heads. In an earlier blogpost, I discussed in detail how the odd spy satellite USA 276 (2017-022A) was set to make a peculiarly close approach to the International Space Station ISS on 3 June 2017. The spy satellite was recently launched for the NRO as NROL-76 by SpaceX, on 1 May 2017.

With the close approach moment now in history and post-approach observations of USA 276 available (as well as an orbit for ISS based on tracking data, rather than an orbital prognosis), I present my final analysis of the situation in the current post.

With the new data included, we can establish the moment of closest approach as 3 June 2017, 14:01:52 UT. It happened over the southern Atlantic north of the Falklands, near 43o.75 S, 45o.45 W, with a miss distance of only 6.4 ± 2 km (the  ± 2 km stems from the fact that TLE predicted positions have a typical positional accuracy of no more than 1 km at epoch).

The latter is significantly closer than the approach distances calculated before the approach (which were in the order of 17-20 km, see my earlier post). Ted Molczan also analyzed the situation and he finds an even closer nominal distance of 4.5 km (but within uncertainty intervals our results overlap).

For the ISS, I used elset  17154.48611204. For USA 276, I used the elset below which I calculated based on amateur observations including my own:

USA 276
1 42689U 17022A   17155.88026473 0.00004763  00000-0  65979-4 0    01
2 42689  50.0047 103.5284 0014136 110.9138 249.3345 15.56256291    00

rms     0.020                             arc May 31.92 - Jun 4.90 UT

For detailed purposes like this, the orbit determination is a bit sensitive to what observer data are included. I restricted myself to observers with known high accuracy in the orbital solution above.

click image to enlarge

click image to enlarge

Below is an updated animation of the situation:

A table of all close approach moments with distances smaller than 500 km:

DATE       UT         km 
3 JUN 2017 02:28:52   478.5 
3 JUN 2017 03:13:37   464.4 
3 JUN 2017 04:01:17   413.2 
3 JUN 2017 04:46:14   398.9 
3 JUN 2017 05:33:41   347.8 
3 JUN 2017 06:18:50   333.3 
3 JUN 2017 07:06:04   282.4 
3 JUN 2017 07:51:26   267.7 
3 JUN 2017 08:38:28   217.1 
3 JUN 2017 09:24:03   202.2 
3 JUN 2017 10:10:52   151.9 
3 JUN 2017 10:56:39   136.6 
3 JUN 2017 11:43:15    87.1 
3 JUN 2017 12:29:16    71.0
3 JUN 2017 13:15:38    26.3 
3 JUN 2017 14:01:52     6.4  **
3 JUN 2017 14:48:01    48.8 
3 JUN 2017 15:34:28    60.5 
3 JUN 2017 16:20:24   112.5 
3 JUN 2017 17:07:05   126.1 
3 JUN 2017 17:52:46   177.5 
3 JUN 2017 18:39:41   191.7 
3 JUN 2017 19:25:09   242.9 
3 JUN 2017 20:12:18   257.4 
3 JUN 2017 20:57:31   308.3 
3 JUN 2017 21:44:54   323.1 
3 JUN 2017 22:29:53   373.7 
3 JUN 2017 23:17:30   388.8 
4 JUN 2017 00:02:15   439.2 
4 JUN 2017 00:50:07   454.5

Note: as positions from TLE's have an intrinsic uncertainty (about 1 km at epoch time), the values in the table above have an uncertainty of about 2 kilometer.

The distance variation around close approach in diagram form:
click diagram to enlarge

click diagram to enlarge

The variation in orbital altitude of both objects around the time of close approach (actual geoid heights):

click diagram to enlarge
As can be seen, USA 276 was a few km (nominally 3.65 km) above the ISS at closest approach. It was nominally also a little bit over 5 km behind the ISS.

In the following diagram, nominal distances in km in X, Y and Z of USA 276 are measured with respect to the ISS. The X is in the direction of movement of the ISS, Y is perpendicular (lateral) to it, Z is the zenith-nadir direction:

click diagram to enlarge

[UPDATE 7 Jun 2017, 15:45 UT, revised 21:14 UT] The variation in position of USA 276 with respect to the ISS was such that it effectively circled the ISS at close approaches, both laterally (cross-track) as wel as along-track, as can be seen in these diagrams below. Please note that, to get a more clear diagram, the axes of the first diagram (crosstrack circling) are not to scale. The second diagram is the same figure, but with axes to scale. The third diagram (along track circling) is also to scale:

click diagram to enlarge
click diagram to enlarge
click diagram to enlarge

A collision avoidance manoeuvre is usually evaluated if an object comes within a box of 4 x 4 x 10 km of the ISS.

If upon further evaluation the chance of collision is larger than 1:10000, an avoidance manoeuvre is done, if circumstances allow this.

USA 276 remained just outside the 4 x 4 x 10 km box at closest approach, as can be seen in the illustration below (red box, the situation shown is for the moment of closest approach). The box represents a collision risk in the order of 1 in 100 000.

USA 276 relative to the ISS proximity safety box . Click image to enlarge  (image made with STK)

I remain agnostic on the question whether this close approach was intentional or not (see discussion in my previous post regarding some possible goals would the approach  have been intentional).

Ted Molczan published a discussion of pro and contra arguments on the question whether the approach was on purpose or not on the Seesat-L list on June 3. While Ted argues that the April 16 and April 30 postponements of the launch indicate a non-planar preference of the orbit (which argues against intention), this also means that this close approach could have been avoided by picking another launch moment.

While USA 276 remained just outside the safety concern box, it is weird to have your just launched classified payload pass so close (6.4 ± 2 km) to a high profile, crewed object like the ISS.

I can and do not believe for a moment that the NRO was not aware that the launch on May 1 would lead to the close ISS approach a month later. It would be extremely sloppy of them, from a Space Situational Awareness viewpoint, if they were not aware, especially given how close the orbital parameters are to that of the ISS.

So I am struggling to understand why the NRO allowed this close approach to happen, if it was not intentional. This event was bound to attract attention and that harms the classified character of the mission. USA 276 is relatively brigh and the approach was bound to be noted by independent observers. Indeed, some space enthusiasts in Europe unaware of the issue who were out to spot DRAGON CRS-11 and Cygnus OA-7 close to the ISS on June 4, did accidentally spot USA 276 passing some 3 minutes in front of it.

It is also an extremely sloppy thing to do because this close an approach to a high profile object like ISS is politically risky. As the ISS is an international cooperation which includes two parties (the United States and the Russian Federation) that are currently geopolitically on an uneasy footing, sending your military payload so close to the ISS as one party is eyebrow raising.

This, and the timing (the close coincidence with the Dragon CRS-11 arrival at the ISS [edit: this refers to the originally planned date of arrival at June 4, later postponed by one day]) was bound to generate questions and suspicions (as it did). What the NRO did with USA 276 in the last few days was therefore really weird.

But then, the current administration of the USA is doing very weird things, and perhaps someone in the new administration signed off on this without fully understanding the depths of it. The Trump administration after all is not quite the posterchild for competence.

(the video below shows a USA 276 pass I filmed in evening twilight of June 4, at low elevation)


lcs said...

I knew even before reading that you would attempt to make some silly political point and you did.

SatTrackCam Leiden said...

Dear Ics.

Good for you. It is my blog, so I can do whatever I like.

In case you haven't noticed in your southern US bubble (I see you are from Virginia): the rest of the world is looking with bewilderment to the giant clusterfuck that is your current US government.

A president that doesn't even know that his own regional military headquarters is in the country he just disavowed and threw to the dogs (Qatar, which is home to US CENTCOM forward headquarters and with this vital to US military activities in the Middle East), and who managed to set up many of his strongest and longtime allies in Europe against him within barely 4 months of his government, is exactly the kind of president under whom's government these kind of weird shenanigans with ISS and the ISS partners do no longer come as a surprise.

It is part of a persistent pattern of not giving a sh*t about his international alliances and of very ill informed and unwise actions by a man who seems to think he doesn't need facts or informed advise before acting.

I have no doubt his administration won't last long, the signs are on the wall for an impeachment. Unfortunately, the damage he is doing to international relations will last long.


fly44d said...

As an American from the left coast, bravo on your political point and response. More Americans need to understand the magnitude of Trump's damage even with his inability to covfefe any legislation and to see the view from outside the country.

Unknown said...

I'm from Virginia. We voted blue fwiw. Covfeve!

Frank said...

And exactly what has the Netherlands ever done for the world? People who talk impeachment are either ignorant of the US Constitution or they have a political axe to grind.

SatTrackCam Leiden said...

@Frank: You should read a history book. We Dutch founded New York, amongst other things. And with France we actually are the oldest ally of the USA. When you lot fought for independance from Britain, we supplied you with arms.

@Unknown: Your president is not just a US citizen's concern, given the role the US plays in geopolitics. Everything he does f*cks us up too.
My axe to grind is not with your political system. It is with the clown you elected as president, and the irreparable harm he is doing.

Oh: and let me remind you both that with $305 Billion per year, the Netherlands is the third biggest foreign investor in the USA. If we stop that, millions of you lose their jobs

the allies said...

Do you prefer Dutch or Deutsch?
Thank the USA if you prefer Dutch.

SatTrackCam Leiden said...

@the allies:
Actually, the Netherlands was liberated by the Canadians.

Also, your comment is completely irrelevant. Not liking Trump does in no way imply that we are not grateful to our allies (not just the USA, but also the British and for the Netherlands notably Canada) for their efforts in WWII.

Rex Block said...

Perhaps it was "practice" for another rendez-vous down the road? It's odd that they would attempt to do something like this, and it is not without risk when you don't have bi-party awareness of the approach of a nearby vehicle. I am sure ISS was not expecting this.

Unknown said...

I think you are forgetting that this mission was authorized by the Obama administration last year, that's why USAF Colonel Jack Fischer (whose background includes time spent at the Space and Intelligence Capabilities Office) was placed on the ISS ahead of schedule. He was supposed to be on the Expedition 52/53 crew, but NASA made an announcement in November of 2016 that he had been "reassigned to join Expedition 51/52 in April of 2017", which conveniently placed him on the ISS just 2 months prior to this "secret" rendezvous. Now, whether the rest of the ISS crew had any idea about the mission, I don't know. But I'm certain, with his top secret clearance and "need to know", Col. Fischer was briefed on this satellite's maneuver.

the allies said...

Oh yes. Thank heavens for Canada.

Mogman said...

SatTrakCam and allied minions,

Trump's book describes in absolute fullness just what he is doing on Twitter, general social media, news media, world politics and world finance.

He is fully aware that no opposing figure will even contemplate buying/reading his writings, none the less, reading them a second time. The man seems a dunce while all the time able to rework anything that needs to be repackaged. The USA actually does need the man's insight and capability to reset its direction. The close proximity of USA 276 really did have a reason. You do not know that reason, never will and that outcome for you reassures me that you have not the foggiest idea of what needs to be done.

So stick to your sat tracking work and leave the hypothetical politics to those of us Americans that raised the money, built the war machinery, trained the trainers, shipped the forces, sent the fuel, made the intelligence, educated the general (Ike) that sent the Canadians that saved your ingrate butt.

USA 276,,,,, yep USA.... and a damn good reason too.

SatTrackCam Leiden said...

Isn't it bloody hilarious that some commenters above need to go back 70+ years to WWII in their efforts to defend the Great Tangerine Leader?

For those weak in the history department, I reitterate that the US Presidents of that time, Roosevelt and Eisenhower, are turning in their graves watching Trump leading their country down the drain. Much of what both have said and done is dramatically opposite of what Trump is saying and doing.

SatTrackCam Leiden said...

@Aratan Aenor,
You make some interesting comments. There seem an awful lot of 'coincidences' around this flyby, enough to make you wonder whether they truely are 'coincidences' or whether you are in need of an aluminum hat.

Some of those coincidences:

1) USA 276 being launched in an orbit such that it was "coincidentally" making a close pass by ISS June 3;

2) It "coincidentally" staying just, but only just, outside the ISS safety box during that flyby;

3) It "coincidentally" in effect circling ISS in two directions due to the orbit geometry at that close encounter;

4) "Coincidentally" Dragon CRS-11 would have arrived the next day, June 4, in the original schedule, with USA 276 still relatively close (close enough to have a good view, distant enough not to endanger the incoming spacecraft), had it not been postponed;

5) And then "coincidentally" it was suddenly decided that Cygnus AO-7 was released from ISS on that June 4, a month ahead of schedule, when Dragon was postponed;

6) "Coincidentally", a few months before, RAVEN, a close approach monitor built by Ball Aerospace, who "coincidentally" also built USA 276, has been installed on the ISS;

7) The astronaut you mention who "coincidentally" served in the Space and Intelligence Capabilities Office, "coincidentally" being bumped up on the list to be onboard ISS while all this happens.

the allies said...

Is it true that the Obama administration signed off on this?
Would be very interesting to know. Wouldn't it?

the allies said...

Did you describe Trump as "Tangerine" based on the color of his skin?
If so, that is quite disturbing.

SatTrackCam Leiden said...

@The allies:
The concept and design of this satellite was certainly born during the Obama administration. But whether this particular mission to the ISS in this form was, remains to be seen. At any rate, with a launch on 1 May 2017, the administration that isued the final "go!" for this mission, was definitely Trump's and as such the end responsibility is his.

And yes, 'tangerine' refers to his unnatural skin colour. Given that Trump infamously openly mocked the disability of a reporter in a very graphic and disturbing way, I see no reason why I should restrain towards him.

the allies said...

The infamous "Two wrongs make a right" theory. Got it.