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, 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 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.


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 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 article.

I am hesitant with regard to accepting the high resolution imaging attempts by Ralph Vandebergh featuring in the 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):

click image to enlarge

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).

click to enlarge
click to enlarge
click to enlarge

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):

click  ap to enlarge

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):

click diagram to enlarge

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.

Monday, 17 December 2018

NROL-71: an enigmatic launch [UPDATED]

(this post on NROL-71 is belated, as I was in hospital around the original launch date. Luckily, launch got postponed)

click map to enlarge

If nothing ontowards happens, the National Reconnaissance Office (NRO) will launch NROL-71, a Delta IV-Heavy with a classified payload, from Vandenberg SLC-6 on 19 December 2018 (18 December local time). [edit:] after the December 19 launch was scrubbed, a new launch attempt will take place on December 20 (December 19 local time in the USA). The December 20 launch was scrubbed as well due to a hydrogen leak in one of the boosters. A provisional new launch date is 21 December 2018 (December 20 local time in the USA) at 1:31 UT.

The new launch date will not be before 30 December 2018.

The launch was postponed three times. Originally to be launched on December 8, a communications problem aborted that launch. A renewed launch attempt the next day, was aborted only 7.5 seconds before lift-off because of a technical issue (see the video below).

A new launch attempt will take place on 19 December 2018 at 1:57 UT. As weather prospects at the moment do not look particularly good for that date, it is possible that the launch will see even further postponement. [edit:] This assessment turned out to be right: the launch was postponed due to high altitude winds. A new launch date has been set for 20 December 2018 at 1:44 UT. The December 20 launch was also aborted, due to a hydrogen leak in one of the boosters. A provisional new launch date has been set for 21 December (20 December local time in the USA) at 1:31 UT. The new launch date will not be before 30 December 2018.

NROL-71 is an odd launch. When the Maritime Broadcast Warnings for the launch came out and revealed the launch hazard areas, they contained a big surprise. The general expectation among analysts was that NROL-71 was the first of the Block V new generation KH-11 ADVANCED CRYSTAL electro-optical reconnaissance satellites. As such we expected it to go in a sun-synchronous, 97.9 degree inclined, 265 x 1000 km orbit.

But the Maritime Broadcast Warnings suggest this is NOT the case. The hazard areas are incompatible with such a sun-synchronous polar orbit. Instead, they point to a (non-sunsynchronous!) 74-75 degree inclined orbit. Not what you expect for an optical reconnaissance satellite!

The map below shows the three hazard zones. Two are directly downrange from the launch site, where the strap-on boosters and first stage splash down. The third area is the upper stage deorbit area (which is remarkably small in size), located northeast of Hawaii, with deorbit occuring near the end of the first revolution (as usual).

click map to enlarge

The trajectory depicted by the dashed line on the map is for a 74-degree inclined, 265 x 455 km orbit. Higher inclined orbits would miss the downrange splashdown zones and the upper stage deorbit area.

Ted Molczan has pointed out that the shift in launch time with each launch delay, points to a specific orbital plane and a specific aim for the rate of precession of the RAAN of -2.27 deg/day.

This is over twice as fast as the RAAN precession of the KH-11 currently in orbit (0.98 deg/day, i.e. sun-synchronous).

This value for the RAAN precession apparently aimed for, puts further constraints on the orbit as in combination with the 74-degree inclination deduced from the location of the Launch Hazard areas it points to a semi-major axis of about 6735 km.

Going from the notion of KH-11-like orbital altitudes, the current typical KH-11 perigee near 265 km would then result in an apogee near 455 km. This is somewhat similar to the orbital altitude of the oldest of the KH-11 on orbit, USA 186 in the secondary West plane, which was in a 262 x 443 km orbit when we last observed it early October (it currently is invisible due to the winter blackout). This apogee would be much lower than that of the two KH-11 payloads in the primary planes, which have apogee near 1000 km, i.e. twice as high, another deviation from expectations. Normally, KH-11 are launched into a primary plane and about 265 x 1000 km orbit, and only after some years, when the payload is moved to a secondary plane (and a new payload is launched into the primary plane), is apogee lowered to ~450 km (see an earlier post here).

So, if NROL-71 is a new electro-optical reconnaissance satellite in the KH-11 series, it represents a serious deviation from past KH-11 missions. The apparent abandoning of a sun-synchronous polar orbit, is surprising, as such orbits are almost synonymous with Earth Reconnaissance. The "why" of a 74-degree orbit is mystifying too. If it does go into a 74-degree inclined orbit, it doesn't seem to be a "Multi-Sun-Synchonous-Orbit".

Alternatives have been proposed. Ted Molczan has for example suggested that, perhaps, NROL-71 could be a reincarnation of the Misty stealth satellites, warning that the unexpected orbital inclination for NROL-71 might not be the only surprise.

I myself was struck by the fact that 74-degree orbital inclination is the prograde complementary of the retrograde 106 degree inclination of the FIA Radar/TOPAZ 6 payload (USA 281,  2018-005A) launched early this year: note that 180-106 = 74. FIA Radar 6 was the first in a new block of TOPAZ radar payloads, just like NROL-71 appears to be the first in a new block of  'something'.

The previous four FIA Radars, launched into 123-degree inclined orbits, were the retrograde complementary in inclination of the prograde 57-degree Lacrosse 5 orbit, another radar satellite. The complementary character of 106-degree versus 74-degree for NROL-71, could perhaps point to NROL-71 being a Lacrosse Follow-On, as a complementary to the newest FIA block.

If NROL-71 is a Lacrosse Follow-On, its orbital altitude and brightness behavious might yield clues: Lacrosse 5 has shown a very distinct brightness behaviour.

It will be very interesting to chase this launch. If launch occurs on 19 December near 1:57 UT and weather cooperates, Europe will have visible evening twilight passes in the first few days.

Below are a couple of search orbits. All are for an assumed 74-degree orbital inclination and launch on 19 December at 1:57 UT. The first three are for KH-11 like orbital altitudes. The fourth is for a Lacrosse-like orbital altitude.

Orbit #70003 fits the hazard areas from the Maritime Broadcast Warnings best.

[EDIT: new updated search orbits below, for the new launch date, 19 Dec 20918 1:44 UT

[EDIT: new updated search orbits below, for the new launch date, 21 Dec 2018 1:31 UT]

NROL-71                                                 265 x 1000 km
1 70001U 18999A   18355.06319444  .00000000  00000-0  00000-0 0    00
2 70001 074.0000 184.7636 0524203 155.2439 326.4145 14.78994708    03

NROL-71                                                  265 x 500 km
1 70002U 18999A   18355.06319444  .00000000  00000-0  00000-0 0    01
2 70002 074.0000 184.7636 0173800 155.2439 324.5345 15.61785606    06

NROL-71                                                  265 x 455 km
1 70003U 18999A   18355.06319444  .00000000  00000-0  00000-0 0    02
2 70003 074.0000 184.7636 0140989 155.2439 324.3567 15.69614809    07

NROL-71                                                  715 x 725 km
1 70004U 18999A   18355.06319444  .00000000  00000-0  00000-0 0    03
2 70004 074.0000 184.8196 0007044 155.2265 327.0336 14.51731413    06

Note that deviations of many minutes in pass time and several degrees deviation in cross-track are possible on all four orbits, certainly several revolutions after launch.

Saturday, 17 November 2018

Modelling the expected orbital lifespan of Orbital Reflector [UPDATED]

Update added 18 Nov 2018, 13:15 UT:
The launch of SSO-A with Orbital Reflector has been postponed, untill after Thanksgiving.

Update added 27 Nov 2018, 12:00 UT: 
New launch date of SSO-A with Orbital Reflector is on 28 Nov 2018 at 18:31:47 UT

Artist impression of Orbital Reflector. Image: Nevada Museum of Art

In just a few days from now, on 19 November 2018 at 18:32 UT, 28 November 2018 at 18:31:47 UT Spaceflight Industry's SSO-A SmallSat Express, a cubesat rideshare mission, will launch from Vandenberg SLC 4 on a SpaceX Falcon 9. SSO-A will release as much as 64 small spacecraft into space, over a 5-hour period, from two free-flying launch dispensers.

Onboard SSO-A is Orbital Reflector, a project by my artist friend Trevor Paglen. It is an interesting object, for several reasons. It is a cubesat that will inflate a large oblong balloon of about 30 by 1.4 meter, a bit shaped like an obelisk. The balloon is made of a very lightweight, Mylar-like foil that is highly reflective. Hence the name: Orbital Reflector. When reflecting sunlight, it should be easily visible from earth.

Orbital Reflector is Art. It is a sculpture in space, one that, in theory, you can see from everywhere in the world (but about reality: see later in this blog post). Trevor teamed up with the Nevada Museum of Art for this project, and it might be the first time a Museum has created an exhibit in Space.

Artist Trevor Paglen and an early spherical precursor prototype of the balloon (now at the Nevada Museum of Art)

Orbital Reflector will be released in a circular, 575 km altitude, sun-synchronous orbit with an orbital inclination of 97.6 degrees. The anticipated moment of release from the Lower Free Flying Dispenser (LoFF) is about 2h 18m (or about 1.5 revolutions) after launch, i.e. 20:50 UT, over Antarctica. At what moment the balloon will be inflated once Orbital Reflector has been released from the LoFF, is unknown to me.

My estimated initial orbit for the object:

1 70000U 18999A   18323.77222222  .00000000  00000-0  00000-0 0    09
2 70000 097.6000 032.4835 0001438 157.1159 325.9970 14.97378736    01

UPDATE (27 Nov 2018):

1 70000U 18999A   18332.77207176  .00000000  00000-0  00000-0 0    00
2 70000 097.6000 041.3000 0001438 157.1159 325.9970 14.97378736    04

... but once the balloon is inflated, the orbit will rapidly change.

The Falcon 9 Upper Stage is deorbited at the end of the first revolution (see map below), near Hawaii. The deorbit-burn might be visible from eastern Europe around 19:50 UT.

click map to enlarge

Orbital Reflector should initially have been launched in the spring, but launch delays pushed the date to 19 November. Unfortunately, due to this and due to the particularities of the orbital plane it is launched into, visibility of the satellite will initially be very bad, and will remain so for weeks.

The satellite will be making late evening passes (around 21:15 local time), remaining in the Earth's shadow and hence unilluminated by the sun in the northern hemisphere. New Zealand, southern Australia and South America in the southern hemisphere may have some spotting opportunity. But for Europe and the USA, initial spotting opportunities will be zero. It is the wrong season to see a satellite in this kind of orbital plane.

So the crucial question is: will Orbital Reflector survive long enough to carry over to spring and early summer, when viewing conditions are more positive? To answer this, I have done some modelling to get an indication of what orbital lifespan to expect.

SRP and modelling lifespans

Orbital Reflector in itself will be an interesting object to follow due to its highly unusual area-to-mass-ratio. Unlike typical satellites (which do experience SRP too but to a clearly lesser degree), this object will be under significant influence of Solar Radiation Pressure (SRP). And SRP will have a clear impact on its orbital lifetime, as we know from both theory and from data on the orbital evolution of earlier inflatable balloon satellites.

Earlier balloon satellites were Echo 1 (1960-009A), Echo 2 (1964-004A), and PAGEOS (1966-056A). Like Orbital Reflector, Echo 1 and PAGEOS were 30 meters wide. Echo 2 was slightly larger at 40 meters. They were spherical in shape, not oblong like Orbital Reflector. They also initially orbitted at much higher altitudes than Orbital Reflector will do: an initial altitude of 4225 km for PAGEOS, 1030 x 1315 km for Echo 2 and  1540 x 1670 km for Echo 1.

Echo 2 during development tests in 1961. Image NASA

The orbital evolution of all these three balloon satellites showed a strong influence of SRP on the evolution of apogee and perigee altitudes. SRP "pushes" and "pulls" on apogee and perigee of the orbit, with a quickly changing orbital eccentricity as a result. The effects can be well seen in the orbital history for Echo 1 and 2 and PAGEOS (source of orbital data used to make these diagrams is JSpOC):

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

A clear pattern is visible where the orbital eccentricity highly oscillates due to SRP. It initially is quickly pumped up, lowering perigee and raising apogee, then gets back to lower values again, and this cycle then repeats.

Something similar will happen to Orbital Reflector. SRP will quickly push perigee down and apogee up, pumping up the orbital eccentricity. The progressively lower perigee at the moments SRP pumps up the eccentricity, will speed up orbital decay.

I used GMAT 2018a to model the effects of SRP on the orbital evolution of Orbital Reflector. That is not something trivial to do, as there are a number of 'unknowns' involved for which I had to make educated guesses. The results below should be taken very cautiously for that reason.

For example, SRP depends on attitude of the spacecraft with regard to the direction of the sun. That attitude will change over time, and there is the question whether the oblong balloon will be (and stay) in stable attitude or start to tumble. SRP in itself creates a torque and might induce tumbling. Issues like these will strongly influence the amount of SRP, drag, and as a result the orbital lifespan. 

There are some uncertainties in the mass of Orbital Reflector as well: depending on whom you ask, it is either 2.2 or 3.2 kg. This is important, because SRP is highly dependent on the area-to-mass ratio (and so is the effect of drag on the object). If the balloon indeed settles in a least-drag orientation after deployment, as the designers expect, the drag surface is a constant 1.97 square meter.

Because Orbital Reflector is oblong, and because of the orientation of its orbital plane with respect to the sun, the SRP surface will vary between (almost) minimum and maximum values over one orbit. I have tried to accomodate this by running the model with an SRP surface that is 50% of the maximum value, i.e. 50% of 21 square meter = 10.5 square meter.

To show the non-triviality of SRP, I first ran the model without SRP, then with SRP, for comparison.

Below are the model results for Orbital Reflector (expressed as apogee and perigee altitude against date) if we ignore Solar Radiation Pressure, for two mass values: 2.2 and 3.2 kg.

model results for a mass of 2.2 kg and no SRP taken into account. Click diagram to enlarge

model results for a mass of 3.2 kg and no SRP taken into account. Click diagram to enlarge

Below are the results if we do implement modellation of Solar Radiation Pressure. The expected lifetime clearly shortens, by up to a third, and this is because of the progressively lower perigee as SRP pumps-up the eccentricity of the orbit. The grey lines in the diagrams are the data without SRP from the previous diagrams, as a reference:

model results for a mass of 2.2 kg with SRP taken into account. Click diagram to enlarge

model results for a mass of 3.2 kg with SRP taken into account. Click diagram to enlarge

These outcomes should be viewed with caution, as the modelling includes educated guesses and, to quote Monty Python, "it is only a model". It will be very interesting to see how the real orbital evolution compares to these model outputs.

What these model results do suggest, is that it is possible that Orbital Reflector, if it inflates and stays intact, might remain on-orbit long enough to carry it into the more favourable part of the year (late spring and/or summer of 2019) for visual sightings. So let's root that my models resemble reality, as I surely would like to see and image Orbital Reflector in the sky.

From the artist impressions, the balloon is flat-sided. This could mean that reflections might be specular, and bright only briefly in narrow zones on Earth, much like Iridium flares.

Sat for Art's sake?

Orbital Reflector is Art. It is distinctly non-utilitarian, in the common sense of that word: it just orbits. But it does have a deeper purpose than that. As Trevor recently put it himself:

"Orbital Reflector was designed as a provocation. An opportunity to think about outer space, the geopolitics of the heavens, and the militarization of earth orbits. It’s a project about public space, and a project about who gets to exercise power over our planetary commons, and on what terms"
In other words, Orbital Reflector is not just there to reflect light to people on Earth; it is also meant to make people reflect, pondering questions such as "who owns space?" and "what is happening out there?".

The question raised by Trevor is pertinent. Space is Public Space. At the same time, it is not public at all, but strongly the domain and playground of Nation States, and notably of the military of those Nation States.

Space is highly militarized. Not so surprising of course as the whole Space Age has its roots in the development of Ballistic Missiles. The role of the military in Space and Space innovation is often overlooked. While many people look at NASA as the big innovator in the US Space program, the real innovations in Space are often the product of another Space Agency, the NRO, which is NASA's shadier military cousin and generally unknown to the broader public, even though it sends billions worth of hardware per year into space. Hardware that plays a prominent role in geopolitics and modern warfare. They include highly detailed optical and radar imaging satellites, navigation satellites, communication satellites and giant listening radio "ears" in space. Long-time readers of this blog know what I am talking about.

Pondering Space and other things. Trevor Paglen (right) and the author of this blog (left), June 2018

It is very interesting that the only areas where it is internationally regulated what can and cannot be done in space, concern weapons in Space and national sovereignty in space. And this was done over 50 years ago already, as part of the 1967 “Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies” (or “Outer Space Treaty” in short).

The fact that after more than 60 years of Space exploration still only the military/national sovereignty aspect has been regulated, tells you how dominant that aspect of the use of space is. Nobody bothered to regulate other potential aspects of space (such as private enterprise).

We are however at a crossroads. Ideas for mining asteroids and for private crewed missions to Mars and the Moon (previously only in the realm of Nation States) have raised the topic of  private enterprise in space, and raised specific questions about regulating the exploitation of resources in Space and protection of historic sites in Space. We are standing at a decisive moment in the use of space too now that purely commercial, privatized space outfits have appeared on the launch market, taking over from companies closely alligned to what Eisenhower called the “Military-Industrial Complex”: new outfits like SpaceX, Rocket Lab and a number of other startups.

But this does not mean that the private sector takes over from the military. Some of these private firms (e.g. SpaceX) have been quickly drawn into the military sphere themselves, with lucrative launch contracts from the US military. Orbital ATK recently has been bough by Northrop Grumman, part of the "Military Industrial Complex" for decades. Meanwhile, three major spacefaring nations, the USA, China and Russia, have increased their military posturing in space, with ASAT tests and increased suggestions within the US military that the US should re-negotiate or even leave the Outer Space Treaty, as it is seen as restrictive to a more active, offensive use of space.

It is therefore a crucial time to bring up questions about who governs space, what is and what isn’t allowed there, who gets to put things up there, and to put to question the overarching role of the military in this all.

Paglen's Orbital Reflector encourages you to reflect upon these issues.

Note: I warmly thank Trevor Paglen, Amanda Horn, Zia Oboodiyat, Mark Caviezel and Ted Molczan for discussions and for providing viewpoints and data.

Edits of 27 Nov 2018: revised launch time, revised elset estimate, new map, and statement that the deorbit-burn might be visible from N-Europe

Tuesday, 9 October 2018

Falcon 9 reentry burn from SAOCOM 1A launch observed from Europe

image (c) Koen Miskotte. Used with permission
click image to enlarge
On 8 October 2018 (7 October local time) at 2:21 UT, SpaceX launched the Argentinian Radar surveillance satellite SAOCOM 1A (2018-076A) in a sun-synchronous ~620 km orbit. The launch took place from launch platform 4 at Vandenberg in California. It was a spectacular launch, yielding spectacular launch images.

An hour later, near 03:40 UT, a bright fuzzy blue object travelling through the sky was seen from northern Europe.

This fuzzy phenomena was the Falcon 9 rocket stage (the 2nd stage) form this launch performing its re-entry burn while passing through apogee, lowering perigee such that it would reenter into the atmosphere over the Pacific Ocean southeast of Hawaii near 04:13 UT, at the end of it's first revolution.

The image above is part of an image taken by a photographic all-sky meteor camera in Ermelo, the Netherlands, operated by Koen Miskotte. It is actually a stack of 4 separate images (hence the three short breaks in the trail), of 88 seconds exposure each, taken between 03:39:30 and 03:45:28 UT on Oct 8, 2018. The bright blue fuzzy streak above the treeline is well visible.

The map below shows the trajectory of SAOCOM 1A during the first revolution. It passed over eastern Europe around 03:40 UT (in making this map I used the orbit of the payload as a proxy, as there are no orbital elements of the rocket stage. At this stage of the launch, the rocket stage will have been close to the payload in a similar orbit).

The map also depicts the deorbit area near Hawaii. The deorbit burn initiating the de-orbit happens about half a revolution earlier (some 45 minutes before reentry) in apogee of the orbit, i.e. over Europe:

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A surveillance camera from a weather station in SüderLügum in Germany, near the German-Danish border, produced this spectacular time-lapse movie of the event (note the "puffs when the rocket engine is firing):

The sky map below shows the trajectory for SAOCOM 1A for Ermelo, the location of Koen Miskotte's alls ky camera (times are in CEST = UT +2). The full all sky image is given as comparison. The two match well:

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image (c) Koen Miskotte. Used with permission
click image to enlarge

Thursday, 27 September 2018

More images of Kounotori (HTV) 7

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The image above is a stack (combination) of six images, taken at 10-second intervals with a 5-second exposure (Canon EOS 60D + EF 2.0/35 mm, 800 ISO). It shows Kounotori HTV 7 (2018-073A), a Japanese cargoship on its way to the ISS launched on September 22. This image was taken some 17 hours before it berthed to the ISS.

The cargoship was about 1m 38s behind the ISS at the time of observation. As no recent orbital elements were available, I did not know where to expect it relative to the ISS, so I started watching well before the ISS pass, and next noted it ascending over the roof just after the ISS had disappeared in Earth shadow.

The HTV 7 spacecraft was very bright during this pass: near magnitude +1, and a very easy naked eye object. Just like the day before (see an earlier post), it flared brightly, to at least mag -1/-2 at 19:50:18 UT (26 Sep 2018). The flare can be seen on the composite image above, and on the single image from this series below:

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Also note the distinct orange colour of the trail, which is due to the fact that HTV 7 is wrapped in gold-coloured insulation foil.

The flare happened while HTV 7 was passing through the field of view of my video setup:

The image below is a composite of the images taken while the ISS passed, and the images of HTV 7 passing 1m 38s later (i.e., they didn't move this close in the sky in reality!). The orange colour of HTV 7 stands out. Also well visible is that HTV 7 was somewhat faster than the ISS, due to a difference in orbital altitude (and hence orbital period):

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Wednesday, 26 September 2018

Imaging a pass of Kounotori (HTV) 7 on it's way to the ISS

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On 22 September 2018 (and after several launch delays, amongst others due to a typhoon), at 17:52:27 UT, Japan's Space Agency JAXA launched Kounotori (HTV) 7, a cargoship destined for the ISS. It will dock to the ISS tomorrow on September 27th.

The 9.8 x 4.4 meter HTV (HTV stands for "H-II Transfer Vehicle". The name Kounotori stands for "white stork") are easily visible, bright objects with a distinct orange colour due to the use of gold-coloured insulation foils.  See the image below of HTV 7 being assembled at the Test and Assembly Building at Tanegashima Space Center before launch:

image: JAXA

After days with bad weather, the sky cleared yesterday. I had a low pass in the southwest near 19:18 UT (Sep 25) and went to the nearby city moat with my camera, as I have a better view lower at the horizon there. Some whisps of thin clouds still lingered in the sky.

First, at 19:04 UT, I watched HTV 7's destination, the International Space Station (ISS), sail past as a very bright object. The image below is a stitch of two image stacks (!): one stack of two images, and a stack of 4 images with the camera FOV shifted horizontally. Camera: Canon EOS 60D with an EF 2.0/35 mm lens. I used exposures of 4 seconds at ISO 800.

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Then  I waited for HTV 7. As the latest orbital elements at that point were almost a day old, I was not sure about the exact time it would show up.

Some 14 minutes after the ISS it emerged, clearing the trees and houses low at the southwest horizon, and to my surprise and joy featured a bright flare to at least magnitude -1. My first image just captured the end of this brief flare (first of the two images below):

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The object was easily visible with the naked eye and had an orange hue. The image stack below was made of 5 images taken at 10-second intervals, with each image a 4-second exposure (camera details the same as for the ISS image). It shows HTV 7 from the bright flare to the moment it disappeared in the Earth's shadow:

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Tuesday, 4 September 2018

Capturing a flaring NOSS duo (NOSS 3-6)

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On 30 August 2018 near 20:59 UT I was imaging the NOSS 3-6 duo (2012-048A & 2012-048P) during a near-zenith pass, when they briefly flared. They were at a sky elevation of 77.5 degrees at that time.

The image above is a stack of the video frames showing the flaring spacecraft: the flare of the leading P component was captured just before it peaked (I was adjusting the camera FOV during the seconds before it), the flare of the A component was captured in its entirety. Below is the video itself from which these frames were extracted (video shot with a WATEC 902H + Canon FD 1.8/50 mm lens):

I next used LiMovie to analyse the video and extract brightness curves from the video frames, with the following results. The data points shown are 3-point averages of the raw data. small discontinuities visible in the curves are where the satellite passed a star:

click diagram to enlarge

click diagram to enlarge

The leading P component seems to exibit only one flare peak. The traling A component shows an interesting  double or tripple peak. The centroids of the peaks of the P and A component were some 6.5 seconds apart.

In the diagram below, I have transposed both curves on each other by shifting the curve for the A component along both axes untill it matches that of the P component:

click diagram to enlarge

What can be seen is that the curve for the A component pre- and post-peak follows the pattern of that of the P component, but unlike the P component it shows a pronounced valley at the peak, with a small secondary peak in the valley bottom. The shape of the valley is the inverse of the peak shape of the P component. Intriguing!

The rather sudden change in steepness some seconds before and after the peaks as shown by both components is interesting too. The main peak shape is slightly asymmetric.

One option for the difference in the shape of the curve for the A component (i.e. for the "valley"at the top) might be the presence of a rotating component interfering with the flare pattern caused by the satellite body, perhaps.

NOSS (Naval Ocean Surveillance System) satellites are SIGINT satellites operated by the US Navy to locate shipping, based on geolocation of the ship's radio emissions. They are also known by the code name INTRUDER. They always operate in close pairs, such as can be seen on the video.

The P component peaked at 20:59:11.85 UT (Aug 30, 2018), at position RA 313.222 DEC +45.628. The A component has a first major peak at 20:59:17.33 UT at RA  313.331 DEC +45.077; the small secondary peak at 20:59:18.37 UT at RA 313.765 DEC +45.307; and a third major peak at 20:59:19.33 UT at RA 314.170  DEC +45.518. The two major peaks are 2.0 seconds apart.

Wednesday, 29 August 2018

The X-37B OTV 5 is manoeuvering to a higher orbit

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The image above shows the classified robottic X-37B space-plane OTV 5 of the US Air Force, a kind of unmanned mini Space Shuttle, in the sky above my home on August 20. It had manoeuvered in the previous days (probably on August 17 or 18), from an approximately 316 km orbital altitude to 325 km orbital altitude, an orbit raise of ~9-10 km. The video below shows it the next night, passing through Delphinus:

Just two days later, on August 22, OTV 5 was a no-show, indicating another, and major manoeuvre. Three days later, Leo Barhorst found it again, and subsequent observations showed it to had moved into a 387 x 395 km orbit. A total orbital raise of some 75 km in series of manoeuvers spanning a few days.

As can be seen in the diagram below, which is based on amateur tracking data, the orbit of OTV 5 had been rather steady from when Cees Bassa first located it in late April 2018 up to mid August, at an orbital altitude of ~316 km. The orbital raises mid and late August to ~325 km and next to ~391 km could point to a new test regime for the experimental equipment onboard.

click diagram to enlarge

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The X-37B (image: US Air Force). Click to enlarge