Sunday, 5 May 2019

Orbital Reflector has joined the Dark Side

image: Nevada Museum of Art

Orbital Reflector will not shine brightly in our night sky. The extraordinary Art project by Trevor Paglen and the Nevada Museum of Art (see my earlier post here) has run on the cliffs of American politics, and was sadly lost as a result.

In a May 1 press announcement by the Nevada Museum of Art, it was indicated that contact with the satellite has been lost, so the command to inflate the balloon can no longer be sent.

That command should have been sent weeks ago, but was postponed because of, basically, the childish state of US politics. The satellite operators needed to have FCC approval to inflate the balloon: approval that should have been given after enough space had been created between the various payloads of the SSO-A launch.

But then, as the Nevada Museum of Art press release puts it:

"two unanticipated events occurred: 1) Due to the unprecedented number of satellites on the rocket, the U.S. Air Force was unable to distinguish between them and could not assign tracking numbers to many of the them. Without a tracking number to verify location and position, the FCC could not give approval for inflation; and 2) The FCC was unavailable to move forward quickly due to the U.S. government shutdown."

The US Government shutdown referred to was the US Federal shutdown imposed by President Trump, when US Congress did not agree to his proposed spending bill for 2019 (notably, the demand for $5.7 billion in funding for his proposed Border Wall). The shutdown lasted until the end of January 2019 (the longest Federal shutdown ever) and affected the functioning of several Federal agencies including the FCC.

As Trevor himself put it recently:

"We needed to coordinate with the FCC to deploy the reflector, but there was no one to take our calls: there was no government".

In the weeks immediately after the SSO-A launch, the Orbital Reflector operators were in radio contact with the satellite. But over time, the radio pings became weaker and by the time the Federal shutdown was finally over and the FCC had resumed functioning again, the radio of Orbital Reflector had fallen silent.

I am very sad about this outcome. I had looked forward to observing and tracking Orbital Reflector, both to admire it as an unusual global piece of art, and to see how its orbital evolution over time would (or would not) match my earlier modelling. I am also sad because I know how much time, energy and thought Trevor, who is a personal friend, has put into this art project, one of his most challenging so far. It is a pitty it worked out this way, even more so because it happened just because of petty US politics, not flaws in the concept.

But even though the original plan was ruined due to a President that was trying to blackmail Congress into submission, Orbital Reflector still serves a goal. One of the goals of Orbital Reflector, besides being seen, was to trigger debate about who owns space, what does and does not belong there, and who gets to decide about that. That debate certainly happened around Orbital Reflector (see a previous post). In that sense, Orbital reflector was a success.

I also like how Orbital Reflector, which was meant to be the very opposite of the dark shady, anonymous and unseen use of space by the military, now has joined the Dark Side itself: unseen, but there, orbiting in anonymity, and in this state as a result of geopolitical power play the effects of which reach all the way into space.

In a way, Orbital Reflector now has become a symbol of how geopolitical powerplay corrupts everything, even Space, which in a  way was the very thing it was intended to make people think about. That's art for you, even if this developed in a way that was not quite foreseen.

Wednesday, 1 May 2019

Why India's ASAT test was reckless (updated)



Today, I published a large article in The Diplomat:

"Why India’s ASAT Test Was Reckless. Publicly available data contradicts official Indian assertions about its first anti-satellite test"

The paper is online here: https://thediplomat.com/2019/05/why-indias-asat-test-was-reckless/

Summary - In this paper, I present an OSINT analysis of data available from Indian and US sources. From missile telemetry data visible in a DRDO released video (!) I reconstruct the last 2.7 seconds of the missile's trajectory relative to the trajectory of Microsat-R, showing that the missile hit the satellite under a clear upwards angle. I also discuss what can be gleaned from the orbital elements of the 84 debris pieces tracked so far.

The main conclusion is that the ASAT test was conducted in a less responsible way than originally claimed by the Indian government. First, the missile hit the target satellite on a clear upwards angle, rather than “head-on” as claimed by DRDO. Second and third, the test generated debris with much longer orbital lifetimes (up to 10 times longer), which ended up at much higher altitudes than the Indian government is willing to admit.

As much as 79 percent of the larger debris fragments tracked have apogee altitudes at or above the orbit of the International Space Station. Most of the tracked debris generated by the test orbits between 300 km and 900 km altitude, well into the range of typical orbital altitudes for satellites in Low Earth Orbit. As these debris fragments are in polar orbits, they are a potential threat to satellites in all orbital inclinations at these altitudes.This threat will persist for up to half a year (rather than the 45 days claimed by the Indian government), with a few fragments lingering on (much) longer, up to almost two years.


UPDATE, 2 May 2019:

On Twitter, I was asked to elucidate a bit more on how I did the analysis.

The delta V calculations have been done using equations from chapter 6 of "Space Mission Analysis and Design", third edition (Wetz and Larson (eds.), 1999).

The missile trajectory relative to the satellite trajectory was calculated with quite simple goniometry from the telemetry values (azimuth, range and elevation from the camera site) extracted from the DRDO video. Azimuth and range allow to calculate delta X, delta Y relative to the camera site on the flat reference plane. Elevation and range allow to calculate altitudes above the reference plane. AS the calculations are done with respect to a flat reference plane tangent to the earth surface at the camera location, this approach is sufficient. Earth curvature and true altitudes above the earth surface are irrelevant, a we are only interested in relative postions with regard to the satellite vector of movement.



Friday, 5 April 2019

First debris pieces from the Indian ASAT test of 27 March catalogued

click to enlarge

Today the first 57 orbital element sets for Microsat-r debris, debris from the Indian ASAT test on March 27, appeared on CSpOC's data-portal Space-Track (I have posted on aspects of this Indian ASAT test earlier: here, here and here). They have catalogue numbers 44117 - 44173. The analysis below is based on these orbital element sets.The elements confirm what we already knew: that Microsat-r (2019-006A) was the target of the ASAT test.

The image above plots the orbit of the 57 debris fragments, in red. The white orbit is the orbit of the International Space Station ISS, as a reference. Below is a Gabbard diagram of the debris pieces, plotting their perigee and apogee values against their obital period. The grey dashed line gives the orbital altitude of the ISS, as a reference:


click diagram to enlarge

Again, it is well visible that a large number of the 57 fragments (80% actually) have apogee altitudes above the orbit of the ISS, well into the altitude range of operational satellites. This again shows (see an earlier post) that even low-altitude ASAT tests on orbiting objects, creates debris that reaches (much) higher altitudes. The highest apogee amongst the 57 debris pieces is that of 2019-006AR at 2248 km.

Below is the apogee altitude distribution as a bargraph (including a kernel density curve), again showing how pieces do reach the altitudes of operational satellites:

click diagram to enlarge

Most of the created debris in the current sample of tracked larger debris has apogee altitudes between 400 and 700 km. It is interesting to compare this to a similar diagram for debris from the 2008 US ASAT demonstration on USA 193, "Operation Burnt Frost":


click diagram to enlarge

The Operation Burnt Frost debris distribution peaked at a somewhat lower apogee altitude, ~250 km (the same orbital altitude as the target, USA 193) while the peak of the Indian ASAT debris apogee distribution is higher, ~400-500 km (there could however be detector bias involved here).

It is interesting to note that both distributions appear to be double-peaked, both having a secondary peak near 700-800 km. I remain cautious however, as that could be due to detector bias.

Overall, the two distributions are similar, as I already expected.

The question now is, how long this debris will survive. To gain some insight into the expected lifetimes, I used Alan Pickup's SatEvo software to make a reentry forecast for the debris fragments. It suggests that most of the debris will stay on orbit for several weeks to months: by half a year from now, most of it should be gone however, except for a few lingering pieces. Note that this forecast should be taken with some caution: it assumes a constant solar activity at the current level, and takes the NDOT values of the element sets face value.

The following bar diagram charts the forecast number of debris objects reentering per week (the x-axis being the number of weeks after the ASAT test) resulting from the SatEvo analysis:


click diagram to enlarge


Again, the result is quite similar to the actual lifetimes displayed by the USA 193 debris fragments after Operation Burnt Frost in 2008 (see an earlier post, with the same diagram), as expected:


click diagram to enlarge

Tuesday, 2 April 2019

Why even low altitude ASAT intercepts are a threat to operational satellites in higher orbits

Click diagram to enlarge. Orbital data from CSpOC

So how big a threat is this Indian Anti-Satellite (ASAT) test of 27 March to operational satellites at higher altitudes, given that it was performed at relatively low altitude (283 km, see an earlier post)?

In an earlier post, I noted that the US ASAT demo on USA 193 ("Operation Burnt Frost") in February 2008 was a good analogue (read here why). Like the March 27 Indian ASAT test on Microsat-r, the USA 193 ASAT demonstration happened at relatively low altitude, even lower than the Indian test: 247 km. So where did debris from that test end up, altitude-wise?

The diagram above is a so-called "Gabbard Diagram" which plots apogee and perigee altitudes of individual debris fragments from the 2008 USA 193 intercept against their orbital period. (apogee is the highest point in its elliptical orbit, perigee the lowest point). The diagram can be of help to show insight into how high fragments are ejected in an ASAT test. Please do note that it concerns a subset of well-tracked larger fragments: most of the smaller fraction of debris, difficult or impossible to track, is absent from this sample.

As is visible in the diagram, many fragments ended up being ejected into highly eccentric ("elliptical") orbits with apogee, the highest point in their orbit, well above the intercept altitude. Many ended up with apogee altitudes well into the range of operational satellites (typically 400+ km).

I have indicated the International Space Station (ISS) orbital altitude (its current perigee altitude at ~407 km, not that of 2008) as a reference. Some 64% of the larger fragments in the pictured sample ended up with perigees apogees (well) above that of the ISS. Quite a number of them even breached 1000 km altitude.

This makes clear that even low altitude ASAT tests generate quite some debris fragments that can endanger satellites at higher altitudes. True, most of it reenters within hours to a few days of the test, but still plenty remain that do not. In my earlier post I showed the orbital lifetime of these same fragments from the USA 193 ASAT demonstration. Many survived on orbit for several weeks to months, occasionally even up to almost two years after the test:

click diagram to enlarge

So it is clear that a "harmless" low altitude ASAT test on an orbital object does not exist (note that I say orbital and not sub-orbital). Every test generates a threat to satellites at operational altitudes. Hence NASA administrator Bridenstine was quite right in his recent condemnation of the test. It is indeed very likely that debris fragments ended up in orbits with apogee at or above the orbital altitude of the ISS and other operational satellites in Low Earth Orbit.

An earlier, failed (?) ASAT test by India on 12 February 2019

image: DRDO

In my previous two posts (here and here), I analysed the much discussed Anti-Satellite (ASAT) test by India taking out Microsat-r on 27 March 2019.  Now the story gets a new twist.

Yesterday, Ankit Panda had a scoop in The Diplomat: it turns out that India attempted an ASAT intercept earlier, on February 12, 2019, which ostensibly failed according to US government sources.

Ankit is well sourced within the US Government, and his sources told him that a missile launch was observed on February 12th, which reportedly failed 30 seconds after lift-off.

A NOTAM and Area Warning had been given out for that day by the Indian government, for the "launch of an experimental flight vehicle" (the latter detail mentioned in the NOTAM but not the Maritime Area Warning). The Indian Government later published a bulletin omitting any reference to a missile failure, instead suggesting the succesful test of an "interceptor missile", launched from Abdul Kalam island, against an "electronic target".


 HYDROPAC 448/2019 (63,71)
(Cancelled by HYDROPAC 485/2019)

BAY OF BENGAL.
NORTHERN INDIAN OCEAN.
INDIA.
DNC 03.
1. HAZARDOUS OPERATIONS 0515Z TO 0645Z DAILY
   12 AND 14 FEB IN AREA BOUND BY
   20-48.07N 087-02.23E, 18-07.27N 086-25.02E,
   01-46.62N 087-30.51E, 02-57.91N 093-50.49E,
   18-33.79N 088-46.21E, 20-48.95N 087-06.99E.
2. CANCEL THIS MSG 140745Z FEB 19.

( 080903Z FEB 2019 )



The hazard area from the Area Warning for Feb 12 is very similar to that of the March 27th ASAT test. Compare these two maps, for February 12 and March 27 (the track shown is the groundtrack of Microsat-r, the target of the March 27 ASAT test. The blue and red areas indicated, are the hazard areas from the Area Warnings):

February 12 Area warning and Microsat-r track
March 27 Area Warning and Microsat-r track.

The hazard areas are virtually indistinguishable, and so is the location of the Microsat-r ground track. Microsat-r clearly was the target ("electronic" or not) of the February 12 attempt as well. Even the pass times are close for both dates: compared to March 27, the Microsat-r pass over Abdul Kalam happend about 1 minute earlier on Feb 12. With the benefit of hindsight, it is all very clear.

Indeed, press reports based on the mentioned Indian Government bulletin give 11:10 am Indian Standard Time (05:40 UT) as the time for the Feb 12 attempt. From the listed time, we can deduce that the virtual intercept would have happend at 271 km altitude, some 12 km lower than the 283 km altitude of the succesful March 27 intercept.

Microsat-r was in a slightly different orbit on February 12th: a slightly more eccentric, but stable 240 x 300 km orbit. During the succesful ASAT test of March 27, Microsat-r was in a slightly more circular 260 x 285 km orbit.

click diagram to enlarge

An open question is whether the February 12 attempt was a rehearsal and not a real attempt to hit and kill the satellite; or if it was a real attempt but failed. If Ankit Panda's US government sources are correct that the missile failed 30 seconds after lift-off, it would seem a failure, unless the cut-off after 30 seconds was intentional. Another open question is whether the US government was aware on February 12 that it was an ASAT test (see also this Twitter thread by Brian Weeden).

With the February 12th attempt so soon after launch of Microsat-r (January 24th), it would appear that Microsat-r was specifically launched to function as an ASAT target.

Sunday, 31 March 2019

Debris from India's ASAT test: how long until it is gone?

click diagram to enlarge

After India's ASAT test on 27 March 2019, on which I wrote in detail in my previous post, many people asked the obvious question related to the debris threat from this test: how long would debris pieces stay on-orbit?

At the moment of writing (late 31 March 2019), no orbits for debris pieces have been published yet, although CSpOC has said they are tracking some 250 pieces of debris currently.

Some insight into the possible lifetimes of debris fragments can however be gleaned from the debris generated by "Operation Burnt Frost", the destruction with an SM-3 missile of the malfunctioned USA 193 satellite by the United States of America on 21 February 2008.

The USA 193 ASAT demonstration in 2008 provides a reasonably good analogue for the Indian ASAT test on Microsat-r on March 27. The orbital altitudes are somewhat comparable: USA 193 moved in a ~245 x 255 km orbit and was intercepted at ~247 km altitude. Microsat-r moved in a ~260 x 285 km orbit and was intercepted at 283 km altitude, i.e. a difference of ~36 km in altitude compared to USA 193. Both intercepts happened in years with low solar activity, i.e. similar upper atmospheric conditions. There are some differences too: USA 193 was intercepted near perigee of its orbit, Microsat-r near apogee. There is a difference in orbital inclination as well: 58.5 degrees for USA 193, and a 96.6 degree inclined polar orbit for Microsat-r. Nevertheless, the USA 193 intercept is a good analogue: much more so than the Chinese Fengyun-1C ASAT in 2007, which was at a much higher altitude and yielded much longer lived debris fragments as a result.

CSpOC has orbital data available for 174 debris fragments from USA 193. I mapped the decay dates of these fragments and constructed this diagram. The x-axis of the diagram shows you the number of weeks after the destruction of USA 193, and the bars show you how many fragments reentered that week:

click diagram to enlarge

The distribution of reentry dates shows that most fragments reentered within two months, with a peak about 3 weeks after the destruction of USA 193. Almost all of it was gone within half a year. Yet, a few fragments ejected into higher orbits had much longer orbital lifetimes, up to almost two years. This shows that even low altitude ASAT tests on objects in Earth orbit do create at least a few fragments with longer orbital lifetimes.

The 174 debris fragments in question constitute a subset of larger, well-tracked particles within the USA 193 debris population. There were thousands more fragments, most very small, that were not (well) detected. Most of these likely reentered within hours to a few days after the destruction of  USA 193, given that small fragments have a large area-to-mass ratio (meaning their orbits decay faster, as they are more sensitive to drag).

Given the similarities, we can expect a similar pattern as the diagram above for debris fragments from the Indian ASAT test. As the Indian intercept occured slightly (about 35 km) higher, fragments might perhaps last a little bit - but probably not that much - longer.


UPDATE (2 April 2019):
A follow-on post with an analysis or orbital altitudes of generated debris can be read here.

Wednesday, 27 March 2019

India's surprise ASAT test of 27 March 2019 (updated)


Click to enlarge. Reconstruction made with STK.

The Indian Prime Minister Narendra Modi made a surprise announcement in the morning of 27 March 2019, claiming that India conducted an anti-satellite (ASAT) test that night under the codename "Mission Shakti".

In the hours after the announcement, some sparse details appeared in Government statements and the Indian press: these included that the launch of the interceptor took place from Abdul Kalam island on the Indian East Coast, and the target was intercepted at an altitude of ~300 km. The missile used was a three-staged missile with two solid fuel boosters. The target satellite was not identified, other than that it was an Indian satellite.

T.S. Kelso, @Dutchspace on twitter and myself were however able to identify the target as being likely Microsat-r (2019-006A), a 740 kg Indian military satellite launched two months earlier, on 24 January 2019, on PLSV-C44 from Satish Dhawan Space Centre. We were also able to determine that the test must have happened near 5:40 UT (27 March 2019).

There are only two Indian satellites that fit an orbital altitude of ~300 km: Microsat-r (2019-006A) and Microsat-TD (2018-004T). Of these, Microsat-r was in a very low orbit (roughly 260 x 285 km). It would also pass right over Abdul Kalam island around 5:42 UT on 27 March 2019.

A Maritime Area Warning for "Hazardous operations" was given out before the test, which in hindsight is likely related to the test:


HYDROPAC 955/19

 NORTHERN INDIAN OCEAN.
 BAY OF BENGAL.
 INDIA.
 DNC 03.
 1. HAZARDOUS OPERATIONS 0430Z TO 0830Z DAILY
 27 AND 30 MAR IN AREA BOUND BY
 20-48.06N 087-02.24E, 18-07.27N 086-25.03E,
 01-46.62N 087-30.52E, 02-57.91N 093-50.49E,
 18-33.79N 088-46.21E, 20-48.95N 087-06.99E.
 2. CANCEL THIS MSG 300930Z MAR 19.//

 Authority: NAVAREA VIII 248/19 221002Z MAR 19.

 Date: 222130Z MAR 19
 Cancel: 30093000 Mar 19



Plotted on a map, it defines an elongated conical hazard area with the tip at Abdul Kalam island. The hazard area fits an object in a polar orbit. Moreover, it exactly fits the track of Microsat-r:

click map to enlarge
click map to enlarge

The fit shows that the intercept might have occured near 5:40 UT, give or take a few minutes, at 283 km altitude while Microsat-r was northbound moving towards Abdul Kalam island. The fit to the hazard area is excellent.

Microsat-r was launched by PLSV-C44 on 24 January 2019, ostensibly as a military earth observation satellite. The satellite was initially in a 240 x 300 km orbit but manoeuvered into a more circular, less eccentric ~260 x 285 km late February.


PLSV-C44 (including Microsat-r) launch. Photo: ISRO

click illustration to enlarge

click diagram to enlarge
click diagram to enlarge

With this ASAT test, India joins a very small number of countries who have shown to have ASAT capabilities: the USA, Russia, and China. The test will certainly cause uneasiness with several countries and provoke diplomatic reactions and condemnation. This is technology many countries do not like to see proliferate, and testing ASAT weapons in space is widely seen as irresponsible, because of the large number of debris particles it generates on orbit, debris that can be a threat to other satellites. Our modern society is highly reliant on satellite technologies, so any threat to satellites (either from ASAT test debris, or by deliberate ASAT targetting) is a serious threat.

In this case, because of the low altitude of the target satellite, the debris threat will be limited (but not zero). Few satellites orbit at this altitude (the ISS for example orbits over 100 km higher). The vast majority of debris generated will quickly reenter into the earth atmosphere, most of it within only a few weeks. But previous ASAT tests like the Chinese Fengyun 1C intercept in 2007 and the USA's response to that, "Operation Burnt Frost" destroying the malfunctioned spy satellite USA 193 in 2008, have shown that a few debris pieces will be ejected into higher orbits, so even at this low altitude the danger of such a test is not zero. Nevertheless, the Indian government seems to have learned from the outcry following China's 2007 test, and they specifically point out the lower altitude of their intercept target, and the lower risk stemming from that.

As to the "why" of the test, there are several answers, some of which can be read in this excellent twitter thread by Brian Weeden. One reason is military posturing towards China. Another one, as Brian points out, is the current emerging call to restrict ASAT tests: India perhaps wanted to have a test in before these calls result in international treaties prohibiting them. Last but not least, the test could perhaps also be a first step towards an anti-ballistic missile system. [edit 30 Mar 2019: ] India already tested an anti-ballistic missile system before, and this can be seen as a next step in building such a  missile defense system.


UPDATE 30 March 2019:

In the press, on twitter and in a message on the Space-Track portal, CSpOC has indicated it is now tracking more than 250 debris pieces from the ASAT test. So far, no orbital elements for debris pieces have been released however.




They also confirm the time of the test as 5:39 UT. In this article, it is indicated that the launch and intercept was detected by US Early Warning satellites, i.e. the SBIRS system of infrared satellites that has been discussed several times previously on this blog.

clickimage to enlarge


click to enlarge

05:39 UT corresponds to the time the satellite first appears over the horizon as seen from the interceptor launch site at Abdul Kalam island: theoretical appearance over the horizon as seen from that site was at 05:38:38 UT.

So I assume the 05:39 UT time corresponds to the moment the interceptor was launched after first detection of the target (assuming a detecting radar located on the launch site), at a range of 8700 km. Indian sources say the intercept, from launch to impact, took 3 minutes. This would place the actual intercept at ~05:42 UT, near 17.68 N, 87.65 E, at an altitude of ~283.5 km and a range of ~450 km from the launch site.

Click to enlarge. Reconstruction made with STK.

The interceptor was a three-staged missile with a kinetic kill vehicle, i.e. a kill vehicle that smashes into the satellite, destroying it by the force of impact. The Indian Dept. of Defense released this image of the launch of the interceptor:

click image to enlarge


Note (31 March 2019): a follow up post discussing likely orbital lifetimes of fragments created, can be read here.

Note 2 (2 April 2019): a second follow up post discussing an earlier failed attempt on February 12, can be read here.

Wednesday, 20 March 2019

No, the failed Venus lander from Kosmos 482 is not about to come down yet


Venera landing craft (photo: NASA)


Late February 2019, a number of news outlets (e.g. here and here) copied a story that originally appeared on Space.com, titled: "Failed 1970s Venus Probe Could Crash to Earth This Year".

It concerned an unusual object launched 47 years ago, called the Kosmos 482 Descent Craft (1972-023E, CSpOC nr 6073). Word was that it was about to reenter into the atmosphere, maybe even this year.  But will it?  Short answer: almost certainly not.

The source of the prediction is attributed to Thomas Dorman in the Space.com article, but how the prediction was done is not clear from the news coverage. On the request of David Dickinson, who was preparing an article on the topic for Universe Today, I made my own assessment of the issue. I looked at the orbital decay of 1972-023E since 1973 and did some GMAT modelling to gain insight into how the orbital decay will develop in the future.

As I will show in this post, my modelling suggests the Kosmos 482 Descent Craft is not to come down yet for several years.


Kosmos 482, a failed Venera mission


During the 1960-ies and '70-ies, the Soviet Union launched a number of Venera space probes destined for the planet Venus. Some of these probes did reach Venus and even briefly took pictures before succumbing to the very hostile atmospheric environment on this planet. But not all of the probes reached Venus. Several attempts went awry.

Kosmos 482, a probe similar to and launched only a few days after the Venera 8 probe, was launched from Baikonur on 31 March 1972. Reaching a highly elliptic parking orbit around Earth, its apogee kick motor failed to put it into an heliocentric orbit. The space probe broke up into at least four pieces that remained in Low Earth Orbit. Two of these, parts of the rocket engine, reentered within weeks of the failure. Another piece, presumably the main space probe bus, reentered in 1981.

A fourth piece, 1972-023E, is left on orbit, and it is interesting, as it most likely concerns the Descent Craft, the lander module in its protective cover that was to land on Venus, similar to the Venera lander module imaged in the photograph in the top of this post. That makes this a highly interesting object, as it will likely survive reentry into the atmosphere (it was designed to survive reentry into Venus' atmosphere after all).


Orbital decay 1973-2019


Initially stuck in a highly elliptic ~9600 x 220 km, 52.25 degree inclined orbit 47 years ago, its orbit has since decayed considerably. Currently (March 2019) it is in a ~2400 x 202 km, 52.05 degree inclined orbit:

click to enlarge

The diagram below shows how the apogee and perigee changed between January 1973 and March 2019. The orbit has become markedly less eccentric. Orbital decay strongly acted on the apogee altitude. The apogee altitude (blue line in the diagram) has come down steadily and by a large amount, from ~9600 km to 2397 km.This lowering of the apogee is to continue over the coming years. By contrast, the perigee altitude (red line) has changed only minimally, from 210 to 202 km over the past 46 years.


click diagram to enlarge

The apogee altitude will continue to come down. Once it is below ~1000 km, in combination with the low perigee at ~200 km. decay will go progressively fast.


Modelling future orbital decay


To gain insight into the validity of the claim that object 1972-023E might reenter this year, I modelled the future decay of the orbit using General Mission Analysis Tool (GMAT) software. Modelling was done for a 495 kg semi-spherical lander module 1 meter in size, using the MSISE90 model atmosphere.

The result suggests that the Kosmos 482 Descent Craft still has at least 5 to 7 years left on orbit. My model has it nominally reenter late 2025. Taking into account the uncertainties, a reentry between late 2024 and late 2026 seems most likely. That is still several years away.

click diagram to enlarge
click diagram to enlarge

The model result fits well with the trend in the actual tracking data, which gives confidence in the results (the thick lines in the diagrams above are actual tracking data, the thinner lines the GMAT modelled future orbital decay. The latter extend the previous trend in the tracking data well, there are no clear pattern breaks).

It should be well noted that modelling the decay of highly elliptic orbits with high apogee and low perigee is notoriously difficult. Yet, both the past and current orbital parameters and my modelling forecast do lead me to think a reentry is not imminent.

I am not the only one casting some doubt on a reentry of 1972-023E this year. Both NBCnews and Newsweek quote earlier results by Pavel Shubin that predict reentry around 2025-2026, quite similar to my results. They also quote well-known and respected space analyst Jonathan McDowell who is similarly opting for a reentry several years into the future, rather than the coming year.


Conclusions 


From my look at the current orbital decay rate and my modelling of future orbital decay, supported by assessments from other sources, it appears that the newsreports suggesting that the reentry of the Kosmos 482 descent craft is imminent and might even occur this year, are in error.

As to the why of the discrepancy: in the Space.com article, Dorman is quoted claiming "Our guess is maybe as much as 40 to 50 percent of the upper spacecraft bus may still be there". It is not clear at all what this "guess" is based on. My own modelling shows that the mass and size of the landing module only (i.e. without other parts still attached), fits the current orbital decay rather well. It is not clear how Thomas reached his conclusion, but modelling with a wrong mass and/or size might explain the discrepancy between my result and that claimed in the Space.com article.

I am hesitant with regard to accepting the high resolution imaging attempts by Ralph Vandebergh featuring in the Space.com article as evidence for object 1972-023E being more than the lander module only, as the weak and rather irregular protrusions visible might be image artefacts from atmospheric unrest and camera shake rather than real structure. Even when telescopically imaged at minimal range in perigee, we are talking about apparent object sizes at the arcsecond level and single pixel level here, conditions under which it is very challenging to image detail. Under such challenging conditions, spurious image artefacts are easily introduced.

Acknowledgement: I thank David Dickinson for encouraging me to probe this issue.

Wednesday, 13 February 2019

USA 290 (NROL-71)

click image to enlarge

The photograph above is not the best of images, but it does show the trail (faint) of  USA 290, the payload of the January 19 NROL-71 launch from Vandenberg. I shot it last Monday morning, February 11th.

I wrote about this odd launch earlier (here). Before the launch, it was widely suspected that this was a new electro-optical reconnaissance satellite, a block V KH-11 ADVANCED CRYSTAL ("Keyhole"). So we expected it to go in a 98-degree inclined, ~1000 x 265 km sun-synchronous orbit, the orbit typical for new primary plane additions to the KH-11 constellation.

But then the Maritime Broadcast Warnings for the launch came out, and it became clear that the splashdown and deorbit zones did not fit a launch azimuth consistent with such an orbit (see a previous post where this was discussed). Instead, it suggested a 74-degree inclined, 265 x 455 km non-sunsynchronous orbit. Which was very odd, as it was completely against expectations for a new KH-11.


click map to enlarge

The launch was postponed several times, but finally happened on 19 January, a month later than it was originally slated. The launch postponements added a new mystery: the shifting launch window times with each postponement suggested a particular orbital plane with a nodal precession of -2.27 deg/day was aimed for.

The question was: why, if  NROL-71 was going into a 74-degree inclined orbit? Targetting a specific orbital plane only makes sense when the payload is part of a constellation of satellites. But NROL-71 was not targetting the orbital inclination of the existing KH-11 constellation (currently consisting of USA 186, USA 224, USA 245). And it's orbit is (as we will see) not sun-synchronous. It is very odd (and does suggest there will be future objects going into a similar orbit).

After launch on 19:10 UT on January 19th, 2019, there initially was no optical visibility as nighttime passes in the Northern hemisphere were in earth shadow.

But radio observers (a.o. Sven Grahn, Scott Tilley, Cees Bassa, Nico Jansen) quickly picked up the radiosignals of the payload at 2242.5 MHz. These showed that the payload was in a 73.6 degree inclined non-sunsynchronous ~400 km Low Earth Orbit, much as we had gleaned pre-launch from the hazard zones in the Maritime Broadcast Warnings.

As USA 290 slowly emerged from Earth shadow passes, the first optical observations were made by Russell Eberst in Scotland in the morning of 1 February. Next Leo Barhorst in the Netherlands soon followed.

These initial passes were very low in the sky, too low for my urban environment where I need elevations above 20-25 degrees to clear the rooftops. And when as February progressed the passes gradually climbed higher in the sky for my location, weather was not cooperating.

But in the morning of 11 February I finally had a clear sky, and managed to image USA 290, photographically as well as on video. As the illumination angle was not the best, the payload stayed a bit faint, but still was bright enough to register as a faint trail on the photograph (the bright star near the trail is gamma Cygni. Image taken with a Canon EOS 60D + EF 2.0/35 mm lens):


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The object showed up well on the video (WATEC 902H + Canon FD 1.8/50 mm lens), yielding good astrometry:




The optical observations helped to better define the orbit. They show USA 290 is in a 393 x 422 km, 73.6 degree inclined, non-sunsynchronous orbit.

Apart from abandoning the 97.9 degree inclined sun-synchronous orbit of the primary plane KH-11's, it also abandoned the 1000 x 260 km orbital altitude that was previously typical for new primary plane launches. The orbital altitude is closer to the extended mission, secondary plane KH-11's, the sole representative of which (USA186) currently is in a 262 x 452 km orbit.

Of course, in terms of orbital inclination and nodal precession (the non-sunsynchronous character) it doesn't compare to any of the previous KH-11.

(Note: a few year ago I wrote a series of detailed posts analysing the orbital constellation of the KH-11, and the typical changes in orbital plane and orbital altitude when a new addition to the constellation was launched: see the posts here and here).


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So, there is something new under the sun, in more than one way. While the general consensus still is that USA 290 is an electro-optical bird in the ADVANCED CRYSTAL lineage, the radical break with previous orbital structures for this series of satellites is highly interesting. It will be interesting to follow this new object, and see how things develop with future launches.

Over the last two years, the black space program in Low Earth Orbit has become much more exciting, with some new eyebrow-raising additions unlike any previous missions. Examples are USA 276, the failed Zuma launch, and now USA 290, all launches from the past 1.5 years.

I like it: just when we thought things were getting perhaps a tad predictable, we are suddenly treated to a number of surprises, resulting in new stuff to ponder and analyse.

Tuesday, 5 February 2019

Doppler curves



The screenshot above is from a new software program I wrote, Doppler 1.0. As the name already suggests, it calculates the Doppler shift of a radio signal from a satellite TLE and downlink frequency for a given receiving station.

It is a Windows program (64-bits) written in the .NET framework and can be downloaded through my website here.

Saturday, 5 January 2019

Fireball seen over New Zealand during cricket match was the reentry of Kosmos 2430 (2007-049A)

image from Fox News broadcast

The image above is a still image from TV-footage shot during the January 5th 2019 cricket match of Sri Lanka against New Zealand at Mount Maunganui, New Zealand. The camera captured a bright, very slow, copiously fragmenting fireball that occurred during the match. Here is the actual footage:




From the video footage, the event had a duration of at last 1 minute, and likely longer. The event was widely seen and reported from New Zealand: more images and more noteworthy video footage, as well as descriptions, can be found in this news article from the New Zealand Herald.

From the footage it is clear that this is a space debris reentry: the event is too slow and of too long duration to be a meteoric fireball.

From a Sri Lankan tv-broadcast of the cricket match, which features a clock in the imagery, the time of the event can be established as 5 Jan 2018 at 07:58 UT (Sri Lanka has a time difference of 5:30 with GMT):

image from Lotus TV broadcast

From the time and location, the event can be identified as the reentry of Kosmos 2430 (2007-049A), a defunct Russian US-K Early Warning satellite launched in 2007. Time and location match well with a near perigee pass of this object over New Zealand. The map below shows its predicted position for 08:00 UT on Jan 5 (movement is from top to bottom):


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CSpOC at the time of writing (5 Jan 2019 14h UT) has a reentry TIP for 6:41 ± 4 m UT on its webportal Space-Track. This is 1h 47m, or one revolution, earlier than the New Zealand sightings.

Nevertheless, I am fully convinced that the event is Kosmos 2430 reentering - the match is too good, and the footage clearly suggests an artificial object reentering from earth orbit. So why the mismatch with the CSpOC TIP?

Kosmos 2430 was in a highly elliptical orbit with perigee over the southern hemisphere. In the diagram below, we see the apogee altitude (the blue line) quickly diminishing in the days before reentry, due to the drag experienced in perigee (diagram based on orbital tracking data from CSpOC):

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The perigee altitude already is very low, near 90-85 km altitude, for days before the reentry and changes minimally untill the actual moment of reentry. The difference between apogee and perigee altitude remains significant up to the last few revolutions, with apogee still at 1000 km only two revolutions before reentry.

This means that, unlike typical objects reentering, Kosmos 2430 only briefly dipped into the upper atmosphere during each orbital revolution, experiencing drag only during brief moments. This is the kind of situation where an object can survive multiple very low perigee passes, and predicting the actual moment of reentry (i.e. during which perigee pass reentry will happen) is difficult. Looking at the CSpOC TIP bulletins for January 5th, this is clear as well as the CSpOC predictions significantly shifted forward in time with the addition of data from each new orbital revolution.

The sightings from New Zealand strongly suggest Kosmos 2430 survived one orbital revolution longer compared to the current (final?) CSpOC TIP estimate.

Note that with such brief but deep dives (well below 100 km) into the upper atmosphere, it is possible that the satellite already developed a plasma tail one or two perigee passes before actual reentry. The copious fragmentation visible in the footage from New Zealand shows that this event, at 7:58 UT was the actual moment of atmospheric reentry and complete disintegration.