Saturday 28 December 2019

Nine months after the Indian ASAT test: what is left?

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Yesterday it was 9 months ago that India conducted its first succesful Anti-Satellite (ASAT) test, destroying it's MICROSAT-R satellite on-orbit with a PDV Mark II missile fired from Abdul Kalam Island. I earlier wrote several blogposts about it, as well as an in-depth OSINT analysis in The Diplomat (in which I showed that the Indian narrative on how this test was conducted, can be questioned).

Over the past year, I have periodically written an update on the debris from this test remaining on orbit. In this post I again revisit the situation, nine months after the test.

At the time of the test, the Indian DRDO claimed that all debris would have reentered within 45 days after the test. As I pointed out shortly after the test in my blogpost here and in my article in The Diplomat, that was a very unrealistic estimate. This was underlined in the following months.

A total of 125 larger debris fragments have been catalogued as well-tracked. Over 70 percent of these larger tracked debris pieces from the test were still on-orbit 45 days after the test (the moment they all should have been gone according to the Indian DRDO!).

Now, nine months after the test, 18 of these debris fragments, or 14 percent, are still on orbit. Their orbits are shown in red in the image in top of this post (the white orbit is that of the ISS, shown as reference).

In the diagram below, the number of objects per week reentering  since the ASAT test is shown in blue. In grey, is a future prediction for the reentry of the remaining 14% of debris. The last pieces might linger untill mid-2023:

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All but four of the remaining pieces currently have apogee altitudes well above the orbital altitude of the ISS, in the altitude range of many operational satellites. Nine of them have apogee altitudes above 1000 km, one of them up to 1760 km. Their perigees are all below ~280 km.

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Saturday 21 December 2019

The stars did not align well for Starliner, it seems

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Yesterday's Boeing CST-100 Starliner Orbital Flight Test was a true nailbiter. This blogpost briefly reitterates what happened, and what could have happened had they not been able to eventually raise the orbit.

Launched atop an Atlas V rocket, this uncrewed inaugural test flight of the new Boeing Starliner crew transport vehicle should have gone on its way to a docking at the ISS today, followed by undocking and landing at the White Sands Missile Range a week from now. The map above which I prepared pre-launch from information in the Starliner Press Kit and Starliner Notebook, shows what should have been the launch track and some keypoints on that track. As we now know, it went wrong at one of these keypoints.

Launch was at 11:36:43 UT. The Atlas V and Centaur upper stage performed fine, the Centaur inserting the Starliner in a 76 x 191 km suborbital trajectory some 12 minutes after launch. Three minutes later, the Starliner separated from the Centaur.

Next, 31 minutes after launch near 12:08 UT, it should have fired its own thrusters, in order to raise perigee and in this way circularize the orbit, becoming truely orbital.

And that went wrong.

Due to a misfunctioning Mission Elapsed Time clock, the Starliner's orbit insertion burn did not go as planned. Initially, an "attitude problem" was reported as well. The next half hour or so was nailbiting, as Boeing and NASA were not quite coming forward with information, apart from the ambiguous comment that the Starliner had "stabilized" its orbit (which is extremely ambiguous wording).

Those of us who know about orbits, realised that if no orbit insertion burn took place, the Starliner would continue on a suborbital trajectory, and reenter with or shortly after the Centaur upper stage (see also the end of this post, where I modelled this). The Centaur reentry was expected to occur south of Australia at about 12:30-12:35 UT (see the map in top of this post), and as the clock approached that time, it became really nailbiting: was the Starliner crew module still on orbit, or breaking up and burning up over the Indian Ocean?

Eventually, it became clear that, many minutes after the original burn time, Boeing did manage to do a burn that raised perigee from 76 to 180 km.

As an interesting sidenote: during the post-launch press conference, Boeing's Jim Chilton seemed to suggest (at 7:25 in below video) that following the timer anomaly, they tried to uplink new commands, but were faced with delays caused by the relay satellite(s) used (TDRS). It also transpired that on a crewed flight, the crew itself would have intervened in this stage:

Orbital data released by CSpOC provided the first unambiguous information to the world about the whereabouts of Starliner. A pre-burn orbit appeared first, showing a 76 x 191 suborbital orbit. As this was pre-burn, this still did not say much about Starliner's state. But shortly after that, a 186 x 221 km orbit was published, somewhat later followed by a new 180 x 221 km orbit. These showed that Starliner had reached a safe orbit around the earth.

The diagram below shows the altitudes of apogee and perigee of the orbit published so far (21 december 12 UT): currently it is in a 241 x 265 km orbit.

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The amount of fuel spent in the emergency manoeuvres after the planned burn did not occur, was thus that it was no longer feasible to reach and dock to the ISS. Over the night, a new burn or series of burns therefore raised the orbit to 241 x 265 km, 58.4 degree inclined, lining it up for a landing at White Sands Missile Range on Sunday 22 December.

The current orbit (epoch 19355.3601887) results in a landing opportunity at White Sands between 12:45-12:55 UT on Sunday 22 December, approaching the range from over the eastern Pacific, as can be seen in the map I prepared below:

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This is based on the current (epoch 19355.3601887) orbit. If new orbit adjustments happen, the projected time of landing might change slightly (e.g. a lowering of the orbit would make the Starliner speed ahead a bit, resulting in a slightly earlier landing time).

[UPDATE 21 Dec 22:15 UT: NASA has announced that the landing will be around 12:57 UT]

What if the orbit raise had failed completely?

Starting from the first, pre-boost orbit released, 76 x 191 km, I used GMAT to model what would have happened. I find that the Starliner, had it continued in that orbit, would have reentered over Polynesia around 12:50 UT,  about 1h 15m after launch, with its first revolution still uncompleted:

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Tuesday 3 December 2019

An interesting CRS-19 Falcon upper stage deorbit area (UPDATED)

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The Maritime Broadcast Warnings with the hazard areas for the upcoming December 4 SpaceX DRAGON CRS-19 supply mission to the ISS have appeared a few days ago.

These include a Broadcast Warning for the Falcon 9 upper stage deorbit area. And that deorbit area (depicted in red in the map above) has an odd position and timeframe:

HYDROPAC 3933/19

DNC 02, DNC 03, DNC 04.
042302Z TO 042344Z DEC, ALTERNATE
052240Z TO 052322Z DEC
58-52S 050-29E, 55-59S 052-23E,
55-26S 059-28E, 54-58S 065-18E,
54-08S 073-22E, 52-46S 083-57E,
51-25S 091-09E, 49-01S 100-13E,
46-34S 108-49E, 44-49S 113-54E,
46-47S 116-19E, 52-02S 109-55E,
52-57S 108-32E, 56-09S 102-10E,
59-05S 092-54E, 61-08S 081-09E,
61-48S 071-27E, 61-08S 060-26E.
2. CANCEL THIS MSG 060022Z DEC 19.//

Authority: PACMISRANFAC 250217Z NOV 19.

Date: 290929Z NOV 19
Cancel: 06002200 Dec 19

With DRAGON CRS launches, the Falcon 9 upper stage deorbit usually happens in the second part of the first revolution, south of Australia or in the southern Pacific. See e.g. the deorbit area for the Falcon 9 upper stage of CRS-17 from May this year, depicted in blue in the map above.

But not this time. The Maritime Broadcast Warning above suggests that the CRS-19 upper stage deorbit happens much later, about 5.5 hours or 3.5 revolutions after launch. In addition, the area is shifted southwards compared to the CRS-19 ground track, indicating a deorbit from an orbital inclination clearly higher than the 51.6 degrees orbital inclination of the DRAGON. In fact, it fits an orbital inclination in the order of of 57-58 degrees, i.e. some 5 degrees higher in inclination.

So that is odd.

The prolonged on-orbit time might be a coasting test with an eye on future missions that require coasting over several revolutions. The indicated inclination change might likewise be a test for a future mission requirement.

I have been entertaining the possibility of an undisclosed cubesat rideshare, to a ~58 degree inclination orbit. But that remains pure speculation and is perhaps not very likely.

Note: in the map in top of this post, the dashed white line is the DRAGON CRS-19 trajectory up to 23:45 UT (Dec 4), the end of the timewindow given by the Maritime Broadcast Warning for the Falcon upper stage deorbit.

UPDATE 4 Dec 2019 10:15 UT:

During the CRS-19 pre-launch press conference yesterday, the SpaceX Director of Dragon Mission Management, Jessica Jensen, said the Falcon 9 upper stage is doing a "thermal demonstration" after the CRS-19 orbit insertion, that amounts to a six-hour coasting phase:

In reply to reporter questions she provided slightly more details somewhat later in the press conference, adding that the test is done at the request of a customer for future missions that require a long coast. During the long coast phase, they will a.o. measure the thermal environment in the fuel tanks. The apparent ~5 degree orbital inclination change was not mentioned: