The Kosmos 482 Descent Craft: imaging an old Soviet Venera probe stuck in Earth orbit

click to enlarge

 

On May 7 I imaged a pass of the Kosmos 482 Descent Craft (1972-023E), using the WATEC 902H camera and a SamYang 1.4/85 mm lens. This is a very interesting object on which I have blogged earlier.

It is the ascend module of a 1972 failed Soviet Venera probe, meant to land on Venus but stuck in Earth orbit after its apogee kick engine failed to push it into Heliocentric orbit towards Venus in 1972. This is the video from (a part of) the May 7 pass of this object:




The object on the video, at that time at an altitude of about 1640 km and range of 1845 km, is about 1 meter large and weighs 495 kg. It should look like this:

photo: NASA. Click to enlarge

The photo above is not Kosmos 482 itself, but an exhibit replica of a sister ship, the Venera 8 landing module in its protective shell. Venera 8 was launched four days before Kosmos 482, and unlike the latter it was successful and did reach Venus.

The failed Kosmos 482 probe still in Earth orbit was launched from Baikonur on 31 March 1972, and put in a highly elliptical 220 x 9200 km parking orbit around Earth. It's apogee kick engine next failed to push it into a heliocentric orbit towards Venus, and the spacecraft then broke up into four pieces.

Three of these four pieces have already reentered, the fourth, that is believed to be the landing module in its protective shell, is still on-orbit and is the object I imaged. It's apogee altitude has been lowering significantly since 1972.  The object will probably reenter somewhere around late 2025 or early 2026: I wrote an extensive blog post about it including a lifetime simulation a year ago.

The diagram below is from that post and shows the observed orbital decay up to March 2019, and the future decay (light blue) that I modelled with GMAT:

click diagram to enlarge

The interesting thing is that the Kosmos 482 Descent Craft might survive reentry largely intact! It is, after all, a lander that was meant to survive ascend through the thick atmosphere of Venus. It's parachute system will probably no longer function (so it will impact rather than land), but we can expect the hardware to reach Earth surface largely intact.

From a Space Heritage point of view, both this and its history makes this 48-year-old piece of Soviet Space hardware a highly interesting object. This is material culture that represents humanities' babysteps in the exploration of other planets.

Which makes this an interesting object to image, from a "Space Archaeology" viewpoint, and an interesting object to keep an eye on the coming years, until it reenters about six years from now.



Added Note,  9 May 2020 13:30 UT:

In response to my statement that the object likely is the lander in its enclosing protective shell, several people have pointed me to telescopic imagery that purportedly would show that a part of the main bus is still attached.

I (and many others in the amateur satellite community - we had a heated discussion on it on the Satobs list a few years ago) distrust imagery of this kind. This is imaging at the edge of resolution, in this case also notably from a non-stable imaging platform (handtracking a moving object at the limit of resolution!). It unfortunately includes cherrypicking frames. It is very difficult to objectively determine what is real detail and what is artefact of the imaging procedure. It is easy to overinterpret.

I also want to note that taking the mass and dimension of the lander only, actually give a very good fit to the observed orbital decay.

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.


UPDATE May 2020:

On 7 May 2020 I imaged a pass of the Kosmos 482 Descent Craft using the WATEC 902H and a Samyang 1.4/85 mm lens. Here is the video:



This is a stack of 564 frames from the video:

Click to enlarge