Wednesday, 6 May 2020

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:

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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 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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