Proton-M rb (2021-066B) reentry forecast (updated)

 (this post is updated when I have run new predictions)

click diagram to enlarge

The Proton-M third stage from the July 21 Nauka launch (see previous post) is coming down fast. The current reentry forecast models place the reentry into the atmosphere in the early hours of August 6 UT.

The diagram above shows CSpOC TIP data in red, and my own GMAT model results in black. My GMAT predictions in tabular form:

DATE         UT    +-        LAT    LON    orbit epoch
6-8-2021     9:55  1.8  day                28-7-2021 12:12
6-8-2021    16:51  1.7  day                29-7-2021 06:01
6-8-2021     9:18  1.4  day                30-7-2021 04:16
6-8-2021     8:29  1.2  day                31-7-2021 05:28
6-8-2021     9:47  1.0  day                 1-8-2021 05:09
6-8-2021    18:23   23  hr                  1-8-2021 22:54
6-8-2021    21:00   23  hr                  2-8-2021 03:19
6-8-2021    13:52   17  hr                  3-8-2021 00:31
6-8-2021    11:44   14  hr                  3-8-2021 16:12
6-8-2021     9:29   11  hr    15 S  177 W   4-8-2021 00:05
6-8-2021     7:50    8  hr    19 N  180 W   4-8-2021 15:44
6-8-2021     6:40    6  hr    38 S  108 W   4-8-2021 23:04
6-8-2021     6:26    5  hr     4 N  146 W   5-8-2021 03:27
6-8-2021     2:56  2.9  hr    25 N  112 E   5-8-2021 12:14
6-8-2021     5:07  2.5  hr    22 S  104 W   5-8-2021 16:37
6-8-2021     5:34  1.7  hr    29 S   24 E   5-8-2021 21:00
6-8-2021     4:49  1.6  hr    32 N  148 W   5-8-2021 21:00*

The last orbit was re-issued with an epoch almost similar to the previous orbit. This orbit is indicated by an asterisk and my final forecast.

Within current uncertainty windows, no meaningful prediction can be given about the location of the reentry yet. The values nevertheless listed in the tabe for latitude and longitude are nominal values only for the middle of the quoted uncertainty interval (which spans multiple revolutions around the Earth). Given the current uncertainty intervals, they are basically meaningless. Only an hour or so before the actual reentry, the uncertainty interval becomes less than one revolution.

The map below shows the nominal GMAT and last pre-reentry CSpOC TIP positions, plus the trajectory over the uncertainty window [EDIT: see update with final TIP at end of post!!!!]:

 

click map to enlarge

The rocket stage has a dry mass of about 4 tons and is about 4 x 4 meter wide. The diagram below shows the evolution of the orbital altitude of the rocket stage so far, based on CSpOC tracking data. Perigee is the lowest point in it's elliptical orbit around earth, apogee the highest point. Altitudes refer to the equatorial radius of the earth.

 

The last few orbits shows signs of trouble in determining the (quickly evolving) orbit (look at the perigee values for the last four orbits issued). The last available orbit was issued in two versions

 

click diagram to enlarge

 

On July 21, a few hours after launch, I filmed the Proton rocket stage during a pass over Leiden, accompanied by three pieces of debris that were never catalogued by CSpOC:

 

(EDIT: see update below movie!)

UPDATE: 

The final CSpOC TIP is in: 4:46 +- 1m UT (August 6) near 37.8 N 155.7 W, north of Hawaii (this is probably based on a SBIRS detection of the reentry fireball, given the very accurate +- of 1 minute).

This is very close to my last nominal GMAT estimate (4:49 UT near 32 N 148 W)! 

In all honesty: given the uncertainty intervals, that very good match is down to pure luck....

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Nauka and it's Proton-M rocketbooster

 

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On 21 July 2021 at 14:58 UT, Roscosmos launched the new MLM-NAUKA module for the ISS from Baikonur, using a 3-stage Proton-M rocket. After its arrival at the International Space Station (ISS) on July 29, it will replace the PIRS module. Docking is set for 13:24 UT on the 29th.

The NAUKA launch came much belated: originally slated for launch in 2007 (!) it was postponed several times, amongst others after a problem with iron fillings in the engine plumbing was discovered.

With NAUKA, also ERA, the European Robotic Arm, was launched.

In order to make room for NAUKA, the PIRS module was undocked on 2021 July 26 near 10:56 UT, and deorbitted (using Progress MS-16 as a 'tug') into the southern Pacific Ocean on July 26 near 14:42-14:52 UT:

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Soon after launch, it became apparent that NAUKA was in trouble. There was an initial telemetry problem, and (very worryingly) the main engines didn't work. Russian flightcontrol eventually used the auxilliary engines to raise the module's orbit.

click diagram to enlarge

For European observers, the first few nights after launch offered good sighting opportunities for the free-flying NAUKA (2021-066A), it's Proton-M 3rd stage (2021-066B), and the ISS, the three on the first evening passing within a few minutes of each other in evening twilight.

The images below show NAUKA and the Proton-M 3rd stage in evening twilight of 22 July, imaged with a Canon EOS 80D + EF 2.0/35 mm lens (first Nauka, then the Proton rb):

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click image to enlarge

The Proton rb, and initially NAUKA as well, were  passing through a very low perigee (initially 187 km for the RB, 195 km for NAUKA) over Europe on the first nights. As a result, they passed at a very high, zipping speed through the sky, which was quite spectacular to see. They were bright too.

The video below shows the Proton RB zipping through a partially clouded Leiden sky at 21 July. In the video, it can be seen that three debris pieces accompanied it (these debris pieces were not catalogued by Space-track). Because of the very fast movement (the rocket stage was at only 187 km altitude at the time!) the video is a bit chaotic: I had to continually adjust the camera pointing:

 

 

This framestack from a part of the video shows the three debris pieces:

I initially had bad luck filming NAUKA: on two evenings I though I had restarted the video camera recording, but didn't. I succeeded on 23 July however:

The videos were made with a WATEC 902H2 Supreme + Zeiss 1.4/35 mm lens.

My current estimate for the reentry date of the Proton-M 3rd stage is within 2 days of August 6, 2021. I will issue regular updates in a new post once we come closer to this date.

Nauka was found to broadcast telemetry on 631.0 MHz. This is a spectogram of signals I received at Leiden, the Netherlands, in the evening of 28 July during the 18:56 UT pass, using an antenna I had quickly whipped up from scratch for this frequency:

 

UPDATE 29 July 13:45 UT:

Nauka successfully docked to the International Space Station at 13:29 UT (July 29) near 45.5 N, 110.2 E at an altitude of 425 km above earth surface.

UPDATE 30 July

It looks like Nauka's long stretch of bad luck continues. After docking, at 16:34 UT (Jul 29) an emergency situation developed when Nauka's thrusters suddenly started to fire on their own, without command, causing the ISS to loose attitude control for a while. Thrusters on the Zvezda module were trying to counter the Nauka thruster's firing, and Russian flight controllers were franticly attempting to get the Nauka thrusters to stop firing. In the end, the situation resolved when Nauka ran out of fuel.

ISS Debris Avoidance Manoeuvre of 3 July 2020

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ROSCOSMOS has announced that the International Space Station (ISS) had to make an unscheduled orbit adjustment (a debris avoidance manoeuvre)  at 18:53 Moscow Time (15:53 UT) on July 3, in order to dodge a piece of space debris. The rocket engine of the Progress MS-14 cargoship attached to the ISS were used for the manoeuvre, burning 100 seconds giving the ISS a delta V of 0.5 m/s. The ISS orbit was raised by about 900 meters as a result.

The brief bulletin did not identify which piece of space debris was dodged. Using COLA, I could however identify it as object 27923 (1987-079AG), a piece of debris from the Russian Proton rocket that launched the Kosmos 1883 GLONASS satellite on 16 September 1987.

One of the rocket stages from this launch shed some 31 pieces of debris in 2003, most of which decayed rapidly. The object that necessitated the July 3 ISS manoeuvre is one of the larger, and one of the few remaining shed pieces on-orbit. It is is a very eccentric, 350 x 4454 km, 64.9 degree inclined orbit (it's apogee has come down considerably over the past 17 years, from almost 20 000 km in 2003). The CSpOC catalogue characterizes its size as 'medium' (i.e. an RCS of 0.1 - 1.0 m²).

Had the ISS not changed it's orbit, this piece of space debris would have made a pass to a nominal distance of ~0.5 km at 18:28:19.07 UT on July 3. Note that this is a nominal value based on two TLE's: so there is a possible error of 1-2 km. But it is clear that this larger piece of debris would have passed well within the 4 x 4 x 10 km safety box around the ISS, necessitating the debris avoidance manoeuvre.

COLA output:

DATE       UT            RANGE   dALT    ANGLE
3 Jul 2020 18:28:09.07   0.5     0.1     107.1

The encounter would have occurred at 436 km altitude over the south Atlantic some 600 km northeast of the Falklands, near 48.1 S,  51.7 W (see illustration above and movie below).

ISS debris avoidance manoeuvres like this are not very frequent: it happens maybe once per 1-2 years.