Spectacular deorbit burn / fuel dump from the Landsat 9 Centaur upper stage observed

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Yesterday 27 September 2021 at 18:12 UT, Landsat 9 was launched from Vandenberg with a ULA Atlas V rocket. 

2h 58m after the launch, after 1.5 revolutions and while over the east coast of the United Kingdom, the Centaur upper stage performed its deorbit burn, lowering perigee such that half an orbit later it would reenter over a designated area in the Pacific Ocean at the end of the second revolution. Following the deorbit burn, there was a fuel blow-out.

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The deorbit burn and fuel blowout happened within minutes of shadow exit over NW Europe. When the resulting exhaust and fuel clouds came into sunlight, they caused a bright spectacle in the sky that was widely seen around 21:12 UT (23:12 CEST) from a.o. the Netherlands, the UK, Belgium, France and Scandinavia.

The event was anticipated: already before the launch, Cees Bassa had noted that the time of the burn coincided with a pass over NW Europe and alerted observers on the Satobs list. I then put out additional alerts on a.o. Twitter, and as a result, many people observed it. 

In addition, there were hundreds of unexpecting casual eyewitnesses, who often had no clue as to what they were seeing. One of the Dutch "UFO"-reporting sites got over 150 reports of a "UFO" in the northern sky as a result.

As seen from my hometown Leiden in the Netherlands, shadow exit would occur low in the northern sky, in Ursa Major. I had put up my camera opposite the historic Leiden Observatory in the center of Leiden, hoping to capture it over the telescope domes.

As it happened, the actual sky trajectory was slightly more eastwards in the sky than we had anticipated based on a pre-launch TLE estimate (my estimate placed in in the tail of the Big Dipper, while in reality it was in the bowl of the Big Dipper). Just enough to place it outside the FOV of my camera (and initially behind a tree). 

So when it became visible and I realized it was off the predictions, I quickly grabbed the tripod and repositioned it. This made me photographically miss the first 20 seconds or so of the event. Over slightly more than 1 minute, I managed to shoot 50 images of the exhaust and fuel clouds descending over the roof of one of the Observatory's auxilliary buildings.

I was lucky with the clouds too. Fields of cumulus were drifting across the sky, and the relevant part of the sky had been clouded out only minutes before the observation (the clouds leaving the scene are visible in the photographs and time-lapse below).

The event was downright spectacular: two v-shaped, comet-like clouds, one very bright and one fainter (see images) with the tips upward, moving down in the sky among the stars of Ursa Major. The brighter, trailing one of the two clouds was easily visible, and of negative magnitude (mag -4 perhaps, as a rough estimate). It's shape changed over time, with a shell-like structure moving away from the tip. Very spectacular!

The fainter cloud is probably rocket engine exhaust from the brief deorbit burn. The brighter cloud is a cloud of fuel particles, resulting from the blow-out (depressurization) of the Centaur's fuel tanks after the burn (this is a.o. done to avoid fuel remnants exploding). Both clouds are illuminated by the sun, which is why they are visible.

Here are some of the 50 images I shot

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In two consecutive of the 50 images, an object briefly becomes visible between the fuel and exhaust clouds (arrow): it is not clear what this exactly is, as one would not expect the Centaur itself in this position (rather, at the tip of the bright cloud).

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Below is a time-lapse movie I constructed from the 50 images. It is at 13 times the real speed: the series of images from which the movie was made spans slightly over 1 minute in time:

The event happened somewhere between ~550 and 685 km altitude, over the United Kingdom and North Sea. An exact altitude cannot be given at the moment: landsat 9 was delivered to a ~685 km orbit, but the rocket made additional manoeuvres, while releasing cubesats.

I have always wanted to see an event like this, and now finally have (my 51 degree North NW European location does not see this kind of events often). Still on my list: a real reentry.

(all the images shown here were made with a Canon EOS 80D camera and EF 2.0/35 mm lens, at 1-second exposure at ISO 2500).

SBIRS GEO 5 Centaur fuel blowout imaged from Australia

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On 18 May 2021 at 17:37 UT, the United Launch Alliance (ULA) successfully launched SBIRS GEO 5 for the US Space Force from Cape Canaveral, using an Atlas V rocket. SBIRS GEO 5 is an Early Warning satellite that detects missile launches (SBIRS = Space-Based Infra-Red System). It was placed in a geosynchronous orbit. Two other small rideshare payloads were also launched on this launch.

Looking at the mission profile, I realized that the fuel blowout of the Centaur upper stage from the launch would be visible from Australia and Indonesia. So I alerted the Seesat-list and also sent a private alert to Paul Camilleri, an observer in Australia who in the past has made spectacular imagery of such Centaur fuel blowout events.

Paul grabbed his camera and went out. And returned with spectacular imagery, which I show here with his kind permission. According to Paul, the blow-out cloud reached magnitude +3.

Paul made his imagery with a Nikon D3200 with an F2.0/85 mm lens. They are 5-second exposures (fixed tripod) at ISO 6400.

In the first image shown, taken 18:55 UT just before start of the blowout sequence, you can see both the Centaur upper stage and the SBIRS GEO 5 payload, which had separated from the Centaur some 40 minutes earlier. In the second image shown, taken 5 minutes later, you can see a V-shaped fuel cloud and a circular ring of blown-out fuel. In the other images, you see further venting, creating a bright V-shaped cloud that slowly dissipated over the next tens of minutes. Paul imaged it untill 19:40 UT.

 

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Paul was not the only one imaging the fuel blowout. Australian astronomer Robert McNaught also captured the event on his all sky camera (image used with permission):

 

 

The fuel blowout happened at about 12000 km altitude. The Centaur upper stage was over the eastern Indian Ocean, just northwest of the West Australian coast at that moment (see map below).

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Fuel blow-outs are done to get rid of left-over rocket fuels in the rocket stage. Venting them into space reduces the risk that vapours from the left-over fuel might ignite (e.g. because of static electricity buildup in the rocket stage) and cause a debris-generating explosion.

Updates:

Animated image sequence by Grahame Kelaher from Australia:

 

Animated image sequence by Tel Lekatsas, also from Australia:

A movie from the all-sky camera of the Edward Pigot Seismic Observatory, courtesy of Michael Andre Phillips in Australia is here (look at the right of the image in the gap in the trees)

USA 310 (NROL-101) and it's Centaur on 25 November

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The image above was taken between 1:28:22 - 1:28:27 UT on November 25, and shows both USA 310 (the NROL-101 payload) and its Centaur upper stage in one image. 

At the moment of imaging they were only some 48 arcminutes apart in the sky. Their real distance to each other was ~541 km. The image was made with a Canon EOS 80D and Samyang 2.0/135 mm lens.

Since launch the Centaur, which is is a somewhate lower, more eccentric orbit than the payload, has gained one complete lap on the payload, and it was overtaking it while I was imaging them in the early hours of  November 25. Their closest approach (at a very safe distance of 533 km) was  a few minutes after the image above, at 1:33:29 UT (25 November 2020).

Note the brightness difference between the two, the Centaur upper stage being clearly brighter than the payload. In this image, the Centaur is near the peak of its periodic brightness variation. In a previous post I have detailed the character of the brightness variation of the Centaur.

Brightness variation of the NROL-101 Centaur upper stage from video observations

 In my previous post I discussed our tracking of the recently launched NROL-101 objects: the payload (USA 310, 2020-083A) and the Centaur upper stage (2020-083B). The latter is variable in brightness (which is one reason why we think it is the Centaur), and I included a preliminary flash period determination of ~140 seconds in that post, based on analysis of my photographs.

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I can now revise this to 138.02 seconds peak-to-peak, as the result of video observations on 22 November. The Centaur was semi-continously imaged over a 23-minute period, covering 10 brightness peaks, with a WATEC 902H2 Supreme and Samyang 1.4/85 mm lens. Photometric analysis with TANGRA yielded the curve above. 

The brightness diagram starts around the time of zenith passage, at an elevation of 87.6 degrees and ends at an elevation of 56.3 degrees. The phase angle changes from 30.6 degrees at the start to 32.3 degrees at the end, the range from 10525 to 11254 km.

The fitted sinusoid gives a peak-to-peak periodicity of 138.02 seconds. The rocket stage varied between roughly magnitude +6 and +8.5 in brightness. The corresponding absolute magnitude, given the range and phase angle, is +2.0 (peaks) to +4.5 (valleys). 

In the first 'valley' in the curve, there is a brief specular flare. Likewise, there seems to be a narrow steep feature on the top of the brightness peaks.

Filming was done at 25 frames/second. A brightness determination was done at every 4th frame. The curve shows 3-point running averages of these determinations.

The calibration from Red magnitude to Visual magnitude is provisional. Gaps in the curve are periods without data, due to e.g. repositioning of the camera field.

MUOS 5 GTO insertion and Centaur fuel dump imaged from Australia

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image (c) Paul Camilleri - used with permission

The spectacular image above was kindly made available to me by Paul Camilleri from Warners Bay in Australia. Taken around 18:03 UT using a 180 mm lens, it shows the just launched MUOS 5 satellite and the associated Centaur upper stage: the latter is venting fuel creating a "comet-like" cloud.

The image was made some 40 minutes after MUOS 5 separated from the Centaur stage (separation happened at ~17:23 UT). The two objects were at an altitude of ~30 000 km at that time, in a Geosynchronous Transfer Orbit (GTO).

Following separation, the Centaur upper stage had made a Collision and Contamination Avoidance Manoeuvre (CCAM) and next started to dump exces fuel in order to reduce the risk of later on-orbit explosions. This fuel-venting causes the comet-like cloud. MUOS 5 itself is visible as a small trail just under the Centaur and its fuel cloud.

Two other classified objects are, by chance, visible in the image as well: Milstar 4 and USA 155. Like MUOS 5, Milstar 4 is a military communications satellite: USA 155 is an SDS data relay satellite.

MUOS 5 was launched today at 14:30 UT (24 June 2016) from Cape Canaveral, using an Atlas V rocket with a Centaur upper stage. For a timeline and details, see here.

Over the next couple of days, MUOS 5 will use its own engines to make a series of orbit raising manoeuvres, followed by an orbit circularization to bring it in a ~5-degree inclined Geosynchronous orbit. Most likely it will initially be placed in a check-out position near longitude 172 W: I observed MUOS 4 in this position last year.

After 5 months or so, when check-out is completed, it will next be moved to longitude 72 E, where it will be parked as an on-orbit spare in the MUOS constellation (see also my earlier post on MUOS 4 here).

MUOS 5 is the fifth satellite in the Mobile User Objective System (MUOS) system of Geosynchronous narrowband communication satellites. The first MUOS satellite was launched in 2012. This system of military COMSAT is to provide communication facilities to 'mobile users': i.e. military personel in non-fixed positions such as ships, aircraft, tanks and vehicles or on foot. It is a replacement for the aging UFO constellation of COMSAT and will be able to be used by legacy UFO equipment.

The MUOS system now consists of four operational satellites (MUOS 1 to 4) and MUOS 5 as said is to function as an on-orbit spare. According to a publication by Oeting et al. in the Johns Hopkins APL Technical Digest 30:2 of 2011, it will be parked at 72 E for this purpose.


I thank Paul Camilleri for permission to feature his splendid image!

Chasing the new NOSS 3-7 pair (the NROL-55 payloads)

NOSS 3-7 (NROL-55) payloads on 2015 October 10, two days after launch
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On October 8th 2015, an Atlas V rocket launched the National Reconnaissance Office's NROL-55 mission from Vandenberg AFB. The mission consisted of two NRO payloads and a number of cubesats hitching a ride. The two NRO payloads (of which only one is acknowledged, the other being catalogued as 'debris', which it isn't) are a new NOSS pair, NOSS 3-7, which replaces the 10-year-old NOSS 3-3 duo (2005-004A and C).

NOSS (Naval Ocean Surveillance System) satellites operate in pairs, flying in close formation. They geolocate ships by radio interferometry observations of the ship's radio and radar signals.

Based on the launch direction and rocket used, as well as the few details published, we knew it would be a new NOSS duo, and from previous launches had an idea in what orbit they would be launched and what manoeuvering sequence would be used.

The first observations of the newly launched objects were made within a few hours after the launch, by several observers. About 1.5 hours after the launch, observers in Iran and Tibet witnessed a spectacular fuel vent by the Centaur rocket from the launch. Next a number of satellite trackers in our network observed the payloads and the Centaur rocket (e.g. here, here, and here).

I was clouded out on Oct 8. I could join in the chase and got my first look at the payloads only on the next evening on the 9th, but under poor conditions (very hazy) with the objects only marginally showing up on my imagery made with a 2.5/50 mm lens.

NOSS 3-7 (NROL-55) Centaur near Altair on 2015 October 10
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The next night, on the 10th, the sky was very clear, and I employed the 1.4/85mm lens rather than the 2.5/50mm lens. First, I imaged a pass of the Centaur rocket near 19:47 UT (image above). As is usual for the Centaur boosters from these launches, it was clearly variable in brightness due to tumbling. This can be clearly seen in the image below, a stack of five images:

NOSS 3-7 (NROL-55) Centaur, stack of 5 images showing brightness variation
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Next I observed the two payloads closely chasing each other near 19:55 UT. Like the previous evening, the leading object was clearly fainter than the following object (movement is from top to bottom in the image below, showing the two payloads crossing a part of Cassiopeia).

NOSS 3-7 (NROL-55) payloads on 2015 October 10, two days after launch
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NOSS pairs operate for about 10 years, each pair maintaining a close spatial proximity configuration of parallel orbits with one satellite just leading the other. After 10 years their mission is over and the pair loses their close spatial proximity. From previous patterns, Ted Molczan expects that the NOSS pair that is being replaced by this new launch (NOSS 3-3, 2005-004 A and C, launched in 2005) will end its mission and lose their close spatial proximity about 7-8 months from now, i.e. around April-May 2016.

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The newly launched NOSS 3-7 duo is not yet at its operational orbit in its operational configuration. Based on past missions, they will continue to manoeuver the next few weeks until they reach their operational orbits (after which a check-out period will follow). This manoeuvering makes them interesting targets to follow the coming few weeks.

The image at the top of this post shows the pair of payloads (moving top to bottom through Cassiopeia in the image), with the leading object being slightly fainter than the trailing object. This is a pattern also seen with previous launches: once operational, both payloads will however be of similar brightness.

Brightness variation of the USA 198 Centaur rocket stage on October 30, 2014

Earlier today I posted this image of the USA 198 Centaur rocket (2007-060B) passing close to M33 galaxy in Triangulum:

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I noted a slight but clear brightness variation in the trail segments on subsequent images (the stack above is a stack of 19 individual images). I therefore decided to use the images to create a brightness variation profile.

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The result is the diagram above (grey crosses are individual pixel values; the blue line is an 11-point sliding average; the red dotted line a sinusoid with a period of 37 seconds). This is the result of combining measurements of the trail brightness variation on 20 images. The individual pixel values are noisy, the result of using a high ISO setting of 2000 (which results in noise) but a pattern is visible, even more so in the 11-point sliding average.

The diagram shows a modest but clear semi-regular brightness variation with a peak in brightness approximately each 37 seconds. There is perhaps also a regularity visible in that each second valley in the curve is more shallow than the first. The pattern suggests a slow tumbling motion.

Below is one of the original individual images:

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Imaging a near-zenith pass of the new NOSS 3-6 pair (NROL-36)

As I wrote earlier, the NRO launched a new pair of NOSS satellites, NOSS 3-6,  on September 13th, as NROL-36. Two days after the launch, I got my first look at these objects, albeit under very poor conditions (see my post here).

Sunday morning, 10 days after the launch, the cloud cover broke and I finally got a renewed and much better view of the two NOSS objects and the Centaur r/b from the launch, during a near-zenith pass. Some very thin cirrus clouds (dispersed aircraft contrails in part) were in the sky. These eerie pictures, taken shortly after 5 am local time on the 23rd, are the result (click them to appreciate them in full glory):

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the NOSS 3-6 duo

the NOSS 3-6 Centaur r/b

The top image shows the payloads, 2012-048A and 2012-048P, traversing Perseus (alpha Persei star association in top). The P-object is leading over the A-object: movement is from lower right to upper left. I could see both payloads naked-eye, at about mag. +4.

Currently, the two satellites are still notably further apart than operational NOSS-es are, as they are still in the process of active manoeuvering. Ted Molczan believes that eventually, the A-object will probably overtake the P-object and become the leading object once the final operational configuration is reached.

The second image shows the Centaur r/b (2012-048N) traversing the Cassiopeia-Perseus border (h and chi Persei in top, stars of Cassiopeia near the bottom). It was very bright, initially +1 just after shadow exit, then +2. I could see no clear periodic brightness variation: the slow tumbling that was apparent in the days right after lauch and which might have been due to remnant fuel outgassing according to Ted Molczan, apparently has subdued.


The USA 237 r/b

On the 16th, I imaged the geostationary satellite USA 237, which is perhaps a 6th Mentor (see the bottom part of my previous post here).

On the 19th, I used the 37-cm Rigel Cassegrain of Winer Observatory (MPC 857) in Arizona to image the USA 237 r/b of this launch (2012-034B) :

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In addition to the USA 237 r/b, I also did one of my periodic observations on Prowler (90-097E) that same night using the same telescope.

April 20 Brazilian fireball was NOT the reentry of an Atlas Centaur r/b

A beautiful, slow, long duration, fragmenting fireball was filmed from Brazil in the evening of April 20 (20 April near 20-21h UT). Movies can be seen here and here.

Soon after the apparition, the question came up: meteoric fireball, or a reentry of "space junk"? Based on the visuals of the two movies available, I noted that it looked like a meteoric fireball, not a reentry.

Subsequently, a piece appeared in Universe Today, claiming it was a reentry: that of an Atlas Centaur rocket, #16102, 85-087B, which launched Intelsat 512 in 1985.

That conclusion is simply wrong however. According to USSTRATCOM the object in question decayed 18.5 hours earlier than the fireball, over the western Pacific at 1:23 UTC (20 April) near 18N, 161 E. It reentered nowhere near Brazil. It did pass over northern Brasil on its final pass an hour before reentry, but that would have been at 00:30 UTC, not 20-21 UTC. Moreover, even that pass would have been too much north to see it from the southern Brasilian location where it was filmed from: it would have passed below the horizon as seen from there.

And even if pieces would have survived longer (highly unlikely in this case), these could not have caused a fireball over Brasil 18.5 hours later: the orbital plane of the r/b was wrongly oriented for that. Around the time of the fireball, any surviving objects in the Centaur orbit would not pass over Brasil but much more north, over Mexico and the Caribean (see below. Note: the object was no longer in orbit at that time!).

So, the object that was filmed was most likely a piece of asteroidal debris, a very nice, very slow and very long duration meteor grazing through the upper atmosphere and breaking to pieces.

Brightness variability of the NOSS 3-3 Centaur Upper Stage (with video)

NOSS 3-3 is a pair of US Navy NOSS surveillance satellites launched early 2005. The Centaur upper stage of this NOSS 3-3 launch, NOSS 3-3r (2005-004B) is still orbiting earth as well. And as it does so, it is tumbling.

This tumbling is visible to an observer as a regular variation in brightness. Currently, the rocket stage brightens up every 11.4 seconds.

Below video shows the regular variation in brightness: watch it go from faint to bright to faint etcetera with an 11.4 second period. It is footage from a pass over Leiden which I filmed in the evening of March 22, using the WATEC 902H and a Canon EF 2.0/35 mm lens:

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Using LiMovie, I extracted the brightness variation from the movie on a frame by frame basis, resulting in the depicted brightness profile above. Note that the tops of the curve are sharp, not rounded. It is a nice saw-tooth pattern. The integrated video frame picture shows the brightness variability nicely too.

Documenting this kind of tumbling behaviour (and notably how it changes over the years) can actually provide some valuable scientific data. A number of amateur observers specialize in these "flash observations", notably my fellow members of the Belgian Working Group Satellites (BWGS).

Two satellite fuel tanks survive re-entry

Two recent finds of satellite fuel tanks - both of carbon-wrapped titanium fuel tanks from the Atlas Centaur upper stages of two US military satellite launches probably - are in the news at the same time. One came down a week ago in Brasil, the other was found in the autumn of 2007 in Australia.

The Brasilian tank (source):




The Australian tank (source):




The Brasilian fuel tank is very likely part of the upper Centaur stage of the rocket that launched a US military communications satellite (Global SATCOM, 2007-046B) in October 2007. The Australian fuel tank could be a part of the upper Centaur stage of the rocket that launched another military satellite, USA 138 (1998-016A) in 1998.