[UPDATED] OTV 6 (USSF 7), the next X-37B launch, appears to go into a 44-degree inclined orbit

OTV 6.  Image: US Air Force. Click to enlarge

If weather cooperates, the next X-37B launch, mission OTV 6 ,also known as launch USSF 7, is slated for May 16, with backup dates on May 17 and 18 in case launch is postponed. The small uncrewed space plane will be launched for the US Air Force by the United Launch Alliance, with an Atlas 5 rocket, from Cape Canaveral SLC-41.

Navigational Warnings have now appeared for this launch, which shed light on the launch window and the orbit aimed for:

NAVAREA IV 388/20(GEN).
WESTERN NORTH ATLANTIC.
FLORIDA.
1. HAZARDOUS OPERATIONS, ROCKET LAUNCHING
   161224Z TO 161453Z MAY, ALTERNATE
   171314Z TO 171532Z AND 181354Z TO 181434Z MAY
   IN AREAS BOUND BY:
   A. 28-36-51N 080-35-57W, 28-41-00N 080-26-00W,
      28-36-00N 080-23-00W, 28-31-36N 080-33-34W.
   B. 32-28-00N 075-12-00W, 33-50-00N 072-51-00W,
      33-08-00N 072-17-00W, 31-45-00N 074-41-00W.
   C. 38-43-00N 062-38-00W, 40-23-00N 058-26-00W,
      39-18-00N 057-47-00W, 37-34-00N 061-56-00W.
2. CANCEL THIS MSG 181534Z MAY 20.//


HYDROPAC 1415/20(74,75).
SOUTHEASTERN INDIAN OCEAN.
DNC 03, DNC 04.
1. HAZARDOUS OPERATIONS, SPACE DEBRIS
   161319Z TO 161528Z MAY, ALTERNATE
   171409Z TO 171607Z AND 181449Z TO 181509Z MAY
   IN AREA BOUND BY
   36-03S 096-54E, 33-40S 098-30E,
   37-32S 108-22E, 40-03S 107-00E.
2. CANCEL THIS MSG 181609Z MAY 20.//


The launch azimuth defined by the three launch hazard areas A, B and C in the Atlantic Ocean and the location of the Centaur upper stage deorbit zone in the Indian Ocean, point to a launch into a ~44-degree inclined orbit, give or take half a degree. The Centaur upper stage will be deorbitted about half a revolution (55 minutes) after launch.

The following map depicts the hazard areas and the trajectory of the first orbit, for a 44-degree inclined orbit and an orbital altitude of ~350 km. The latter orbit fits the locations of the hazard zones well, and the ~55 minutes time difference between the start of the launch windows and the start of the Centaur upper stage deorbit windows in the Navigational Warnings combined with the position of the deorbit zone, fits a ~350 km altitude orbit:

Click map to enlarge

Launch into a 44-degree inclined orbit unfortunately means I do not get to track it from the Netherlands, as my observing location is too high north in latitude to see it in such an orbit. Following the previous OTV 5 launch, that went into a 54.5 degree inclined orbit and could be well observed from the Netherlands, I had some hopes for OTV 6, but alas no, it is not to be apparently...

A 44-degree orbital inclination would be similar to mission OTV 3 from 2012-2014. These are the orbital inclinations of all past OTV missions:

Mission     inclination    operational period        flight duration
OTV 1       40.0^o          22/04/2010 - 30/11/2010   224 days
OTV 2       42.8^o          05/03/2011 - 16/06/2012   468 days
OTV 3       43.5^o          25/10/2012 - 17/10/2014   675 days
OTV 4       38.0^o          20/05/2015 - 07/05/2017   718 days
OTV 5       54.5^o          07/09/2017 - 27/10/2019   780 days
OTV 6       44.0^o ?        16/05/2020 - ?

With regard to the upcoming launch, the given launch windows for May 16 and the two backup dates are curious. These launch windows are not the same duration (May 16 is 2h 29m in duration; May 17 is 2h 18m in duration; and May 18 only 40 minutes in duration).  They shift oddly from date to date too. The start of the given windows shifts 50 minutes between May 16 and 17; and shifts 40 minutes between May 17 and 18. It moreover shift to a later time between consecutive dates: while a given targetted orbital plane would make the launch shift to an earlier time, not a later time

Perhaps this is done to obfuscate the launch time and RAAN aimed for (or maybe it is just simply Range availability at play). If we look at the common ground: all three launch windows have a potential 10-degree wide RAAN window between 331^o.14 and 341^o.17 in common, so perhaps that is what is aimed for. If that interpretation is correct, this would lead to the following potential 40-minute launch windows, shifting back by 4 minutes each day:

16 May     13:58 - 14:38 UT
17 May     13:54 - 14:34 UT
18 May     13:50 - 14:30 UT

But of course, it is always possible that they launch straight away at the 12:24 UT opening of the May 16 window...we will see!

[Edit 15 May 2020 23:20 UT: but see note at end of post!]

A lot has been written about the X-37B and its purpose, and there are a lot of persistent misconceptions regarding the fact that it is a "space plane" (see my blogpost "X-37B fact and fiction" from July 2019).

Far from being a nefarious device, the X-37B appears to be a testbed for experimental space technology. According to the US Space Force, one of the things that will be tested during the next OTV 6 mission is an experiment to transmit solar power by microwave. It will also contain two NASA experiments that study the effects of radiation on materials and seeds, and it will deploy at least one military cubesat, FalconSat 8 (the previous OTV mission, OTV 5, released three cubesats).

The US Space Force Press Release also indicates that, as a first, OTV 6 will be fitted with a "service module" to the aft of the vehicle, that will house experiments (previous OTV missions housed experiments in the cargo bay). It will be interesting to see what happens to this service module at the end of the mission.

Addendum 13 May 22:05 UT:
More on the microwave experiment in this article (HT to Brian Weeden). It seems it is not so much transmission by microwave, but the generation of microwaves from solar power, which is then send through a cable, if I get it correctly. Anyway: something with microwaves...

Addendum 15 May 23:20 UT:

Bob Christy wrote a very interesting analysis on his Zarya blog, in which he links similar odd jumps in past OTV launch windows to times of close KH-11 passes, the idea being that these KH-11 satellites image the OTV after launch to see whether everything is allright. If that is correct, then this leads to four possible launch times on May 16: 12:24, 13:15, 14:06 and 14:53 UT.
My estimated elsets for these four launch times can be found here.

Addendum 18 May 13:55 UT:

OTV 6 launched on 17 May 2020 at 14:13 UT. A pre-launch estimated elset can be found here;  a preliminary radio-observation based orbit here.

Based on the preliminary radio elset, OTV 6 appears to have been inserted into a 45-degree inclined orbit at ~390 km altitude. The ground track repeats every 3 days:

click to enlarge

Here is how the launch track based on the radio orbit (red dashed line) compares to my pre-launch estimated launch track based on the locations of the hazard areas from the Navigational Warnings (blue dashed line):

click map to enlarge

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

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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.

Imaging the new Iranian satellite NOUR 1 (2020-024A) [UPDATED triple]

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On 22 April 2020 around 4:00 UT, Iran's Islamic Revolutionary Guard surprised the world by launching a military satellite. The satellite is named NOOR 1. The name 'NOOR' means 'Light' in Pharsi.

The object is designated NOUR 01 by CSpOC, with catalogue number 45529  and Cospar designation 2020-024A.

NOUR 1 was launched using a new 3-stage Qased rocket from Shahroud (36.200 N, 55.334 E), the first Space Launch from this facility.

Little is known about NOUR 1, but the fairing of the Qased rocket depicted what looks like a 6U cubesat, i.e. a small satellite with a bus of roughly 10 x 20 x 30 cm in dimension (not counting any deployed solar panels):

The satellite deployed in a 427 x 435 km, 59.8 degree inclined orbit. The orbit is not sun-synchronous, but does have a repeating ground-track about every 4 days.

Three days after the launch, on 25 April, I managed to image the Upper Stage of the Qased rocket that launched the satellite, with a WATEC 902H camera and Samyang 1.4/85 mm lens:





Attempts to image the payload itself (NOOR 1) initially failed, because the late April/early May passes for my location were not the most favourable concerning illumination angles and sky elevation (these passes were low north for me).

But last night, May 6 around 1:52:11 UT, I had a more favourable pass and clear skies, and successfully managed to image the payload NOOR 1 with the WATEC 902H camera and a SamYang 2.0/135 mm lens. As this camera/lens combo has a small field of view (FOV), the observed arc is short: about 4 seconds. Here is the video:





The satellite was at a range of 595 km and a sky elevation of 46 degrees in the south-southwest at the time of the observation. I estimate it to be around magnitude +7.5 in the imagery.

The satellite shows no clear brightness variation during the captured 4 seconds, as is also visible from this 100-frame stack of the video frames:

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It should be noted that there is footage from May 3rd obtained by Paul Maley in the US which does seem to show some variability. But Paul's footage is very noisy, making interpretation difficult [edit: but see below!]:

(footage by Paul Maley)

At any rate, my own observation from last night does not show clear signs of tumbling, but I'll be monitioring the payload further the coming nights to look for any variability.

-----

UPDATE 7 May 2020

New observations from the night of 6 on 7 May do show brightness variation. The satellite was filmed during a near-zenith pass with the WATEC 902H and a Samyang 1.4/85 mm lens.

Below image is a stack of 126 video frames (representing 5 seconds of footage) shwoing a brightness variability with a peak-to-peak period of about 3.2 seconds:

click to enlarge

Here is video footage from alst night: the framestack above is from the first of the 3 shown sequences:



So the satellite is rotating, at the least (note that rotation can be intentional, e.g. spin stabilisation). So far it does not seem to be wildly tumbling, but I will continue monitoring and adding more data.

[end of update: continuation of original post below]

-----

Why this interest in potential tumbling behaviour? There has been speculation about the state of the satellite, following derogatory remarks shortly after the launch by the US Chief of Space Operations, General Jay Raymond, who called it "a tumbling webcam in space" (and says its a 3U cubesat):

@US_SpaceCom continues to track 2 objects @PeteAFB’s @18SPCS associated w/#space launch from Iran, characterizing NOUR 01(#SATCAT 45529) as 3U Cubesat. Iran states it has imaging capabilities—actually, it’s a tumbling webcam in space; unlikely providing intel. #spaceishard

— Gen. Jay Raymond (@SpaceForceCSO) April 25, 2020

US military sources are clearly trying to imply that the satellite is a failure, but that seems a politically inspired stance. My own optical imagery from last night, as presented here, has no indication for tumbling: if it tumbles at all, then it is at a very slow rate. neverthless, the new data from May 7 do show that the satellite is at least rotating.

Moreover, during the three weeks after the launch, several amateurs including myself have received strong telemetry signals from the satellite at 401.5 MHz, consisting of regularly spaced data packets with one data packet sent each 10 seconds.

The signals were first detected and identified as coming from NOUR 1 by Scott Chapman, and the story of this identification can be read in this highly informative blogpost by Scott Tilley which also points to some interesting aspects of the signal, which can be partly decoded (!).

Below is a spectrogram of the telemetry signals as received by me from Leiden, the Netherlands, during a pass in the evening of  30 April 2020: note how strong and regular the signal is:

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The Doppler curve of the signal matches that for NOUR 1 well, so there is little doubt this signal comes from the Iranian satellite.

(note: the spectrogram also shows the signal of a second satellite at 401.5475 MHz, 'Object F', which is an unidentified cubesat from a Chinese launch in December 2019)

Radio amateurs closer to Iran have reported data dumps when the satellite is in reach of Iranian ground stations. So clearly, the satellite is alive and relaying data of an unspecified nature.

At the end of the first week of May, reports have been coming in that detected signals were weakening or absent. This could indicate that after 3 weeks of functioning, the satellite has developed battery problems. On the other hand it could also mean that after a check-out phase the satellite has been shifted to operational mode, and might only be sending while over Iranian groundstations. Further monitoring should shed light on this.


UPDATE  6 May 2020, 18:50 UT:

 I monitored the NOUR 1 pass of 18:42 UT (May 6) and can confirm that the telemetry signal at 401.5 MHz is no longer present.

Perhaps the satellite has completed checkout and is now in operational phase, which could mean it only sends when in range of Iranian groundstations.

UPDATE 9 May 2020, 20:55 UT:

After Iranian sources indicated the 401.5 MHz frequency would be used again for a few hours on the night of May 9/10, I indeed had positive observations of the telemetry signal again on 9 May during the 18:09 and 19:45 UT passes. Here are a screenshot, full spectrogram, and Doppler-curve fit (blue line: theoretical Doppler curve for NOUR 1. Black dots: observations).

This means the satellite is still alive and the absence of the 401.5 MHz signal for a week was because it was in another operational mode, switching to another frequency.

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Guest Post: Modelling of Starlink trail brightness and comparison to observations

(The following post is a Guest Post written by Richard Cole)

Observers have been reporting ‘missing passes’ of Starlink trains since the Starlink L1.1 launch, the first of the operational spacecraft. A missing pass is where an examination of the NORAD or SpaceX orbital elements, or a prediction from one of the Starlink websites, would indicate that multiple spacecraft should be expected to be visible but none appear on time.

An observer in Argentina noted missing passes to their south in late February, local summer. Initially, I thought that perhaps the spacecraft had been temporarily placed into the operational low brightness mode (that brightness having been seen on the prototypes after deployment in mid-2019) but this did not match other observers seeing the same spacecraft at normal brightness at similar times. This phenomenon affected spacecraft in the holding orbit at 350-380km, not the operational spacecraft at 550km.

Recently, the images of the spacecraft on-orbit by Ralf Vandebergh and Szabolc Nagy showed its large solar panel of the solar array was facing the Earth when the spacecraft were overhead and explained the normally high brightness of the spacecraft as seen from the ground. The longer dimension of the panel was observed to be parallel to the velocity vector of the orbit, i.e. the orbit path.

SpaceX had referred in communications to a low-drag mode which was consistent with the observed appearance. This raised the question of how this mode of operation would deal with acquiring enough solar power. Would the panel always face upwards to the zenith, or would the spacecraft be rolled around the velocity vector to get more sunlight onto the panel?

During April 2020 more observers saw missing passes. I had personally tweeted a prediction for a late evening pass of the Starlink L1.5 train to the north of my site in southern UK on April 20th, but the spacecraft were only magnitude 6, needing binoculars to be seen at all. Observers in northern UK reported they had visually seen spacecraft on that pass. It was clear that the spacecraft were indeed being rolled around the velocity vector and by such an angle they were nearly directly facing the Sun, now towards the north in Spring, and observers to the south were just seeing the shadowed back of the panel.

Since it was clear that further analysis was needed to accurately predict visible passes, early on April 21st I created a simple model of the spacecraft panel pointing axis assuming the panel long axis was the velocity vector and the spacecraft was being rolled so that the Sun was in a plane normal to the panel and through the long axis (figure 1). Usually the panel cannot directly face the Sun, but is at some offset angle, in azimuth and elevation.

Figure 1: Spacecraft Roll-Angle concept.  Click diagram to enlarge

This concept allows calculation of the angle between the direction the panel is pointing and the observed Starlink direction for a particular observer on the ground, for the same time. This ‘panel view angle’ will be different for each possible observer of the same spacecraft at the same time, some will see a large part of the sunlit side of the panel, some will see only a little of the same side and some will see only the back of the panel away from Sun, which is dark.

The model gave panel view angles consistent with recorded occasions of observed train non-appearances.

Marco Langbroek’s excellent observation and images of the L1.5 train from Leiden on 2020 April 21 (the same day as the first version of the model was written, as it turned out) provided a useful test of the model. Further, more recent information from SpaceX has confirmed this behaviour and suggested that the actual roll-angle used on-board many not be exactly as calculated above.

In the image below (figure 2) I plot the calculated glancing angles to the sunlit side of the solar panel (so a glancing angle of zero means the view angle of the panel is to the edge of the panel, an angle of 90 would be face on). I have done this for two altitudes (elevations) in Marco's image, 50° and 70°. The roll-angle was as calculated above.

Figure 2: Marco Langbroek's image of Starlink 5 passes, with the calculated panel glancing angles overlaid. Click to enlarge

The trend of a reducing glancing angle with Starlink brightness is correct, so as the Starlinks passed further north (to the right of the image) of Marco at Leiden, less and less of the panel sunlit surface was visible until nothing could be seen. There was one predicted Starlink that passed on the right of the image (further north) but is only detectable by image analysis, it can’t be seen in the original camera image because very little of the sunlit side was facing the camera:

Figure 3: the extra and faint track of a predicted Starlink satellite in the image. Click to enlarge

I was observing the same pass from southern UK a few minutes earlier than Marco and saw the same behaviour of reducing Starlink brightness as each Starlink passed further to the north. I was very pleased to see he had recorded it in his image.

However, the fit is not perfect so I tried changing the roll-angle by a small amount from that calculated. The fit was best for a deviation of nine degrees from the model, that is the actual roll-angle was nine degrees less that the simple model predicts and the panel is pointing slightly higher in the sky. This gave a better fit:

Figure 4: the same image with the changed panel glancing angles overlaid, using an offset of nine degrees in the solar panel pointing direction. Click to enlarge

SpaceX is now promising to change the roll-angle model used on-board to minimise the Starlink brightness as seen from the ground. The panel will be rotated, at periods when the Starlink can be seen from the ground, so the sun falls on the edge of the panel, not on its face as in figure 1. This is a small portion of each orbit and as Starlinks at low altitude are not using their communication equipment, they will need less power to keep functioning.

Richard Cole
Twitter: @richard_e_cole

The reentry of the Soyuz r/b 2020-026B over Spain and Portugal

This morning, Jon Mikkelson (@Itzalpean) drew my attention to this Twitter message:

Meteoro sobre A Coruña pic.twitter.com/OHa6dNfYmA

— Israel Borja Nuñel Timiraos (@Canaan_1983) April 28, 2020

The movie was shot from A Coruña in NW Spain this morning (28 April 2020) around 6:45 local time, which equates 4:45 UT. It clearly shows space debris reentering and breaking up.

Here are a few screenshots from the video:

A brief look in the CSpOC TIP messages showed a very clear candidate: 2020-026B, the upper stage from the Soyuz rocket that launched Progress MS-14 to the ISS on 25 April.

The CSpOC TIP lists the reentry for this object at 4:45 +- 1 minute UT for 28 April, near 38.4 N, 15.5 W, west of Portugal. This matches both time and location of the Spanish movie well.

Below is a map I created showing the final revolution of this rocket stage. The red circle is the nominal CSpOC position for the reentry (we suspect these "+-1 minute" positions are based on SBIRS detections). A Coruña where the video was shot is also indicated in the map.

Note that an observer in A Coruña looking towards the trajectory would see it move from right to left (towards the east), and this matches the video. Also note that while CSpOC gives an instantanious time in its TIP messages, reentries in reality take some time (several minutes). The object would pass A Coruña about 2 minutes after the nominal CSpOC time, which is well within a typical reentry duration.

click map to enlarge

Addition 17:15 UT (28 April):

For clarity: the trajectory above was created by taking the last available orbital elements for 2020-026B (elset 20119.06935500) and evolving these to a final decay orbit with SatEvo.


Here is a second video of the event:

Starlink Galore! [UPDATED]

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Last week was dominated by impressive - if worrying - displays of SpaceX Starlink satellites. Over several nights, objects from the 18 March 2020 launch (Starlink 5) made impressive passes in the sky. And on April 22, there was a new launch, Starlink 6, that could be well observed in the evening of the 22nd and 23rd, causing an impressive satellite 'train' on April 23.

In this blogpost I provide photographs, video, and descriptions.

The new launch on April 22 (Starlink 6)

On 22 April 2020 at 19:30 UT, SpaceX launched the 7th Starlink batch of 60 satellites, Starlink 6, from SLC 39A on Cape Canaveral. Some 23 minutes later, the newly launched objects made a pass over the Netherlands, in a blue twilight sky, and were well visible.

Just some seven minutes prior to this pass, and 15 minutes after launch, the payloads had been deployed from the Falcon 9 Upper Stage while the latter was over the Northern Atlantic.

With the naked eye, the Falcon 9, the just released satellites and the associated debris objects all looked like one bright object (mag 0 to -1) crossing the sky. In binoculars, they could be separated into multiple objects.

The photograph below is a stack of 12 photographs, 2.5 seconds exposed each with a Canon EOS 80D and EF 2.0/35 mm lens at F2.2, 400 ISO, showing it pass over my house in Leiden.

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In 10 x 50 binoculars, the view was spectacular. It consisted of a bright object (the Falcon 9 upper stage), slightly separated from another, elongated bright object (the clump of released satellites), and four fainter flashing objects surrounding them in a paralellogram shape. These were the four tumbling retaining rods that had held the satellite stack together before deployment.

Some of this is visible in this video I shot with the WATEC 902H and FD 1.8/50 mm lens. Falcon 9 and payloads still appear merged as one object here, but the retention rods are visible as separate objects:




The provisional orbit that I had calculated prior to the launch turned out to be quite good: the objects were only 28 seconds early on predictions and less than 0.5 degrees off-track at culmination.

The next night, April 23, saw a twilight pass of the satellites again, that by now had developed into a clear 'train' of objects. They were not as bright as in May 2019 with Starlink 0.1, but in 10 x 50 binoculars the moving string of 60 lights, some 10-15 degrees long, was impressive. While low in the west, in Orion, they briefly became bright and clearly visible to the naked eye for a few seconds, then they grew fainter and I turned to my binoculars to observe them.

My WATEC 902H video camera, this time equipped with a Canon EF 2.0/35 mm lens, captured the train passing in Hydra. The video gives a good impression of the view as it was visible in binoculars:




The next day, April 24, I also filmed the 'train'. This was a low pass (21 degrees maximum elevation) in twilight, at rooftop level, shot from the loft window of my home. Video withe the WATEC 902H and a 1.8/50 mm lens:

Starlink 5 passes, April 19-21

Earlier that week, we were treated on some spectacular, if eerie and worrying, displays of Starlink satellites from the previous launch, the Starlink 5 launch on 18 March.

(worrying, because of the implied impact on the night sky)

A month after launch, the objects from this launch are dispersing as they one-by-one are lifted to a higher orbit, but mid-April there was still a recognizable main group that took about 20 minutes to pass. When passing south of the zenith they are bright (but faint when passing north of the zenith, due to satellite orientation and sun-satellite-observer angles), on the first few passes even very bright (up to magnitude +0.5 for almost a full pass).

At any given moment during the pass of this group, there were 5-8 bright satellites moving in the sky at the same time, following each other in file, typically some 20 degrees apart. It was a very eerie sight reminiscent of a Science Fiction Movie: almost like the Mothership had unloaded the invasion fleet into earth orbit! The long duration, 20 minutes that satelite after satellite after satellite appeared in file, made it very impressive.

Here is a single photographic image from 19 April, showing 4 Starlink satellites traversing the sky (the fainter one that is somewhat off-set is already rasing its orbit). It is a 5 second exposure with an EF 2.0/35 mm lens on a Canon EOS 80D:

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Below is a stack of 202 images from 21 April, showing 39 Starlink satellites that appeared over a 20-minute period. Note how the trails become fainter when located more north (image is looking west, so north is at the righthand side of the image). Also note the two flaring satellites:

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Here are single images showing the two flaring satellites, Starlink- 1274 and Starlink-1309, flaring close to Pollux:

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I used the 202 photographs, shot over a 19-minute period,  to create this time-lapse movie showing the steady stream of satellites:




This is another time-lapse video, from images from the deep-twilight pass of the previous night, 20 April:



Below are three more stacks of photographic images from April 19 and April 20 (the gaps in the trails are the brief moments between two consecutive photographs, hence the dashed appearance of the trails):

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Starlink "train" photographed from the International Space Station

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The image above (image ISS062-E-148365, original at high resolution here) was shot from the International Space Station (ISS) on 13 April 2020, 21:25:02 UT. It shows the Aurora Australis (southern lights) and a train of SpaceX Starlink satellites.

The presence of the Starlink train in this image was first noted by Twitter user Riccardo Rossi (@RikyUnreal) and brought to my attention by Huub Eggen (@phi48). It is present in two earlier images as well, taken the preceeding minute (images ISS062-E-148363 and ISS062-E-148364).

ISS was at 48.25 S, 81.03 E and 440 km altitude at the time the photo above was taken. With this information, I came to the following probable satellite ID's (annotations in image below) for the objects in the imaged "train": these are all objects from the 17 February 2020 launch ("Starlink 4").

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One year after India's ASAT test

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Today it is one year ago that India performed an ASAT test codenamed 'Mission Shakti'. The test consisted of the on-orbit destruction of the Microsat-R satellite (2019-006A), launched specifically to function as target for this test. The intercept occurred at 285 km altitude, but created debris pieces with apogee altitudes much higher than that. I have earlier published an extensive OSINT analysis of the test in The Diplomat of 30 April 2019.

The test generated large amounts of debris. A total of 125 larger debris pieces have been tracked and catalogued by the US tracking network. Note that these only concern larger pieces: most of the generated debris probably was too small to be tracked.

Over the past year I have periodically posted an update on the status of these larger debris pieces on this blog. Whereas the Indian DRDO claimed at the time that all debris would have been gone 45 days after the test, the reality has been quite different: 45 days after the test, 29% (less than a third) of the larger debris pieces had reentered. It took 121 days for half of the pieces to reenter, and some 200 days before 75% of the tracked debris pieces had reentered.

One year after the test, some 114 of the tracked debris pieces have reentered according to CSpOC tracking data. And two more objects for which no decay message was published by CSpOC, 2019-006AR and EA, have reentered according to my own analysis with SatEvo, bringing the total tally of reentered larger tracked pieces to 116.

Nine, or some 7%, of the original 125 larger tracked debris pieces are still on orbit.

It concerns objects 2019-006V, AJ, AX, BD, DC, DD, DE, DM and DU (red orbits in the image below: the white orbit is that of the ISS, as a comparison).  They have apogee altitudes varying from 600 to 1500 km, and perigees generally near 260 to 280 km. Six of these are expected to reenter over the next half year 9 months. And the last debris pieces may not reenter before 2022-2023.

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SpaceX's Starlink Darksat is, indeed, darker

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The image above is a composit of stacked frames from four video sequences shot in the evening of March 22. Apart from a stray Chinese rocket booster that happened to cross the field, it shows four Starlink satellites from the 2020-001 launch: Starlink-1114 (2020-001P), Starlink-1030 (2020-001N), Starlink-1084 (2020-001B) and Starlink-1098 (2020-001D). These satellites are currently at their intended operational altitude.

Starlink 1030 is also known as DARKSAT - it is the Starlink satellite that has been given an experimental coating to reduce its brightness.

As can be seen in the video stack, the coating indeed seems to reduce the brightness. The effect is also very apparent in the photographic imagery below, comparing Darksat to two other operational altitude Starlink satellites in the same orbital plane, Starlink-1114 and Starlink-1084 that both passed within 5 minutes of Darksat. The two regular Starlink satellites are well visible, but Starlink-1030 Darksat is very faint in the image:

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The video images were taken with a WATEC 902H and Canon FD 1.8/50 mm lens at 25 fps. The photographic images were taken with a Canon EOS 80D + EF 2.5/50 mm lens at 1000 ISO, 10 seconds exposure.

It is difficult to attach reliable magnitudes to the video and photographic imagery, but I'd say the magnitude difference between Darksat and the others is probably in the order of 1 to 2 magnitudes. Given their shape, the brightness which Darksat and other Starlink satellites can attain will probably be  highly depending on the viewing angle (as well as of course the phase angle at time of observation), i.e. which part of the satellite you are looking at.

Dragon CRS-20, 23 minutes after launch, with thruster firings

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SpaceX launched the Dragon CRS-20 cargoship to the ISS this morning at 4:50:31 UT. Some 23 minutes after launch from SLC-40 at Cape Canaveral in Florida, it was visible from the Netherlands around 6:13 local time (5:13 UT) in morning twilight. There were some fields of clouds in the sky, but I nevertheless got a clear view of the four objects associated to the launch, all still closely together.

The image above is a 2-second exposure at 800 ISO which I took during the pass, using a Canon EOS 80D DSLR and a SamYang 1.4/85 mm lens. The image shows the trails of  four objects, two of which are tumbling. In the annotated image below, I identify what is what:

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The Dragon cargoship, the Falcon 9 upper stage and the two solar panel covers were easy naked eye objects. The Dragon and Falcon 9 upper stage were very bright and steady, while the two solar panel covers slowly flashed alongside them. These solar panel covers varied in brightness between invisible (with the naked eye) and magnitude +1.5. The Falcon 9 upper stage and Dragon were about +1.5 to +2: with the naked eye, being very close together they seemed one object, while on the photographs they are clearly two.

The image below, taken a few seconds after the previous image, shows one of the tumbling, slowly flaring solar panel covers at its brightest, rivalling the Dragon and Falcon 9 upper stage in brightness:

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The slow regular flashing behaviour was nice to see: the two tumbling solar panel covers were alternating, when one of the two was bright, the other was faint (clearly visible in the image above and the video below). Due to the alternatingly flashing panel covers above and below the Dragon, it looked a bit like an aircaft.

I also captured a small part of the pass on video, using the WATEC 902H with a 1.8/50 mm lens on a fixed tripod in autonomous mode (I was outside myself witha sceond tripod and the photo camera). In this video segment (below), a thruster firing is visible as a cloudy upwards moving "puff"starting at 5:13:00 UT:



Dragon CRS-20 will berth to the ISS on Monday 9 March near 11:00 UT.

This was the last flight of a Dragon 1, and the concluding flight of a contract awarded in 2008. All future Dragon supply flights will be done by an updated model, the Dragon 2 as well as the crew-rated Crew Dragon variant of the latter.

Launching cubesats from the X-37B OTV 5: lifetime modelling with GMAT

image: USAF

Last week, CSpOC issued catalogue entries for three cubesats released as part of the X-37B mission OTV 5.

It concerns USA 295 (2017-052C), USA 296 (2017-052D) and USA 297 (2017-052E). No orbital data are given, but the catalogue entry did explicitly indicate that all three are no longer on orbit.

That cubesats were released as part of this X-37B mission had been clear from a US Air Force statement made after completion of the OTV 5 mission in October last year. The wording of that statement is however ambiguous: while most analysts take it to mean the cubesats were released by OTV 5, it is also possible that they were released as ride shares by the upper stage of the Falcon 9 rocket that launched OTV 5 in 2017.

In this blog post, I will do an academic exercise aimed at guessing when, at the latest, these cubesats could have been released by OTV 5, assuming release from the latter.

OTV 5, the 5th X-37B mission, was launched from Cape Canaveral on 7 September 2017. It landed at the Kennedy Space Center Shuttle Landing Facility on 27 October 2019, after 780 days in space. Unlike previous missions that were all launched in 38-43 degree inclined orbits, this one was launched into a 54.5 degree inclined orbit. Combined with the fall launch date, this meant it took our tracking network a while to locate it on-orbit: the first positive observations were made in April 2018, half a year after launch.

From April 2018, when we started to track it, to October 2019, when it landed, OTV 5 orbitted at various orbital altitudes between 300 and 390 km altitude (see diagram below):

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The CSpOC catalogue entry lists all three cubesats that were released as part of this mission as "no longer on orbit". Assuming they ended their orbital life by natural decay (rather than, for example, being retrieved by OTV 5 again at a later stage, which is in theory certainly possible!), the fact that they were no longer on orbit by 11 February 2020 might yield some constraints on when they could have been released.

To get some idea of the orbital lifetime of a cubesat released from OTV 5, and spurred on to do so by Jonathan McDowell, I ran several GMAT models in which I modelled a 5 kg 3U cubesat released at three altitudes: 400 km, 360 km and 325 km.

We do not know the actual orbital altitude of OTV 5 at that  moment. Nor do we know when the cubesats were released. Hence the three altitude variants. The start point of the modelling was an assumed release into the OTV 5 orbit on October 7, 2017, one month after launch of OTV 5.

For each cubesat, the models were run in two variants: one with the cubesat in minimal drag orientation (0.01 m² cross section), and one with the cubesat in maximal drag orientation (0.03 m² cross section). I used the MSISE90 atmosphere in the model, with historic Space Weather data for October 2017 to February 2020 and estimated solar and geomagnetic activity parameters from the 'early cycle' variant of the GMAT Schattenfile for dates past early 2020.

For the three assumed orbital altitudes and an assumed release one month after OTV 5 launch, the GMAT data produce the orbital decay plots below. In these plots, the red data are for minimal drag orientation, the blue data for maximal drag orientation. If the cubesats in question were similar to NRO's Colony II cubesats, then the red minimum drag orientation curves probably represent the orbital evolution best. If they were more like Colony I cubesats, then the blue maximal drag curves are more representative.

Taking the minimal drag variants, and under the assumption that the cubesats were 3U cubesats and not retrieved on-orbit by OTV 5 at a later stage, the suggestion is a release below 350 km. Released at higher altitudes, they would still be on-orbit.

Assuming reentry before 11 February 2020 after natural orbital decay, a minimal drag orientation and release no lower and no higher than 325 km, the latest possible moment of release would be late August 2018, give or take a month to account for the uncertainties.

It appears we can rule this out however, because we know that OTV 5 was orbiting at 380 km altitude, not 325 km altitude, at that time. So the best guess (although one under many assumptions) is a release some time before August 2018, i.e. within 1 year after the launch of OTV 5.

It is still possible that the cubesats were released at a later date, but next retrieved while still on-orbit by OTV 5. If the cubesats were smaller than a 3U cubesat, a later release than August 2018 is possible as well.

Finally, given the ambiguity in US Air Force Statements on the matter, it is also possible that the cubesats were released from the Falcon 9 upper stage on the day of launch.

For more about the X-37B, and especially the active myth-making that seems to be at play around this secretive space-plane, see my earlier post here.

OTV 5 rising in April 2018. Click image to enlarge

Iran's failed Zafar launch: where did it go?

Zafar-1 launch on 9 Feb 2020. image: IRNA

On 9 February 2020 at 15:48:15 UT, Iran tried to launch a new satellite, Zafar-1, on a  Simorgh (Safir-2) rocket. Video released by the Iranian government shows that lift-off was succesful, and so was first stage separation and second stage ignition around 15:50:00 UT, and fairing separation around 15:50:18 UT. The upper stage next however failed to reach the necessary speed to put the satellite into earth orbit.

The intended orbit according to Iranian sources was a 530 km altitude, 56-degree inclination orbit. Orbit insertion however failed because the Simorgh upper stage burnt out at a speed of 6.533 km/s, almost 1 km/s short of the necessary 7.4 km/s,  according to the Iranian minister of Communications and Information Technology, Mohammad Javad Azari Jahromi. The upper stage and satellite reached an apogee at 541 km altitude before making a long ballistic flight back to earth surface.

Zafar 1 on top of the Simorgh rocket at Semnan. Photo: IRNA

In order to get some idea where it's flight ended, I have modelled the failed launch in STK and GMAT.

The ascend to 541 km altitude was modelled in STK, with launch into the azimuth needed to reach a 56.0-degree orbital inclination (launch azimuth about 134.7 degrees - this was calculated with software I have written myself). I positioned apogee such as to correspond with an attempted orbit insertion about 10 minutes after launch (a typical value for launch into lower LEO). Burnout speed was put at 6.533 km/s, per Iranian sources.

The resulting State Vector was then used as input in GMAT to model the ballistic descend. I did this for two cases: for a 90 kg mass, ~0.25 m² cross-section object corresponding to the Zafar satellite; and for a 1000 kg mass, 4.5 m² cross-section object corresponding to the spent Simorgh upper stage. As I had no values for mass and size of the latter, I used values similar to a North Korean UNHA-3 upper stage. The MSISE90 atmosphere with current Space Weather was used in GMAT.

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The result of this modelling is impact in the Indian Ocean some 25 minutes after launch and some 6400 km downrange from Semnan, at about 12 S, 88 E, for both the satellite and the Simorgh upper stage (see map above). These values should not be taken too strictly, given several uncertainties in the model input: they are ballpark figures.

As it turns out in this case, varying the mass and size have mostly minor effects on the impact position only (note: in an earlier modelling attempt posted on Twitter, the impact point came out closer to Iran, because in that initial model run I had been using a lower burnout speed).