TOPAZ/FIA Radar 5, the NROL-47 payload

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The small streak in the center of the image above in a bright blue, partially cloudy twilight sky, is TOPAZ/FIA Radar 5 (2018-005A, 43145), the NROL-47 payload (see a previous post) imaged in evening twilight of 19 January 2018 with the sun at only 8 degrees below the horizon and the satellite at 24 degrees elevation in the northwest.

NROL-47 was launched on 12 January 2018, a week before the photo above was taken. Shortly after launch, Cees Bassa and Scott Tilley already detected the payload by radio, determining a preliminary orbit from the Doppler curves with an orbital altitude near 1057 km and inclination near 106 degrees.

The first optical observations were done in the evening of January 14th, two days after launch, by Cees Bassa in the Netherlands, after which it was picked up by a number of other observers as well (amongst others Leo Barhorst in the Netherlands, Greg Roberts in South Africa and Paul Camilleri in Australia). The latest optical observations have improved the orbit for this new satellite and show it is in a 1048 x 1057 km, 106.0 degrees inclined orbit.

The payload was making very low (11-12 degrees maximum elevation) twilight passes in the north during the first few days after launch for my locality, where I have obstruction from buildings. Passes gradually climbed higher in the sky over the week, but also deeper into twilight. Combined with dynamic weather, I started to lose hope of imaging it, but finally was succesful in the evening of 19 January. I had a 24 degree maximum elevation pass in the southwest near 17h UT, with the sun barely 8 degrees below the horizon. The pass was high enough to clear rooftop level near culmination.

The weather was again very dynamic that evening, with fields of clouds forming as soon as the sun set. Using the 1.4/85 mm lens, I took a series of images while clouds were moving in fast. Due to the very bright sky background, I was restricted to 1 second exposures at 400 ISO.

After a first quick cursory check of the images on the camera's LCD screen I initially thought I had lost the battle against clouds and twilight. But upon a more thorough inspection on my laptop a day later, it turned out it was in the images after all, and with enough reference stars to get some decent astrometry from the images.

The payload is in a new orbital plane for TOPAZ/FIA Radar satellites. While all previous four TOPAZ/FIA Radar satellites are in a 123.0 degree inclined orbit, this new TOPAZ/FIA Radar 5 is in a 106.0 degree inclined orbit.

I had already inferred a new orbital plane for this satellite pre-launch (see a previous post), based on the launch azimuth, which deviated from that of previous TOPAZ/FIA Radar launches from Vandenberg. The new 106.0 degree orbital plane is within 2.5 degrees of my original pre-launch estimate. The orbital altitude is somewhat lower than I initially estimated.

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Operating in two orbital planes was also the case of a previous series of radar satellites, the Lacrosse (ONYX) satellites, of which currently only Lacrosse 5 is still in orbit. These operated in two orbital planes, at 68 and 57 degrees orbital inclination.

The 123.0 degrees orbital inclination of TOPAZ/FIA Radar 1 to 4 is the retrograde equivalent of the 57 degree inclination of the Lacrosse constellation. The new 106 degree orbital inclination is however not the equivalent of a 68 degree inclination.

The current TOPAZ/FIA Radar 5 orbital altitude of 1048 x 1057 km is slightly lower that that of the previous four TOPAZ/FIA Radar satellites, which orbit at ~1100 x 1110 km. However, it is not unlikely that over the coming weeks the orbit will be further raised to a similar altitude.

Unfortunately, I am now losing visibility of the object as the higher passes occur deeper and deeper in twilight.

TOPAZ-5 is the last of the block I TOPAZ payloads. The new 106.0 degree inclined orbital plane might be the new orbital plane for the block II payloads to be launched over the coming years.

What is NROL-47 and in what orbit will it be launched? [updated twice]

UPDATE 10 Jan 17:25 UT: The launch has been scrubbed due to high altitude winds, and moved one day to Jan 11. New start of launch window is given as 1 pm PST = 20:00 21:00 UT. This means the launch window is shifting, indicating a prefered orbital plane and launch probably right at the start of the launch window.

Update 12 Jan: The launch was again scrubbed yesterday, and is now slated for January 12, 21:00 UT . My remark about a  shifting launch window above was in error, I missed that the Maritime Broadcast Warning window opens somewhat before the actual launch window opens.

Final Update , 12 Jan: NROL-47 successfully lifted off from Vandenberg SLC-6  at 22:11 UT!

Final Update 14 Jan 2018: Amateur observers using radio have located NROL-47 in orbit. It is transmitting in the TOPAZ frequency, 2241.52 MHz. The orbit is still very preliminary but appears to point to ~1100 km orbital altitude and an orbital inclination of ~105-106 degrees. This would identify NROL-47 as a new TOPAZ, but in an orbital plane that differs from the previous four TOPAZ satellites. Due to bad weather at the observing sites of several of our active observers (I was clouded out yesterday evening myself for example), optical observations have not yet been reported.

Hot after the excitement and drama of the Zuma launch (see my previous post), a new classified launch is upcoming on Wednesday January 10, when ULA will launch NROL-47, a classified payload for the National Reconnaissance Office (NRO), on a Delta IV from Vandenberg SLC-6 in California.

From Maritime Broadcast Warnings, the launch window opens at 20:30 UT and closes at 01:26 UT. [edit 1] After a one-day delay due to weather conditions, the launch is now slated to be on the 11th of January with the launch window opening 21:00 UT. The shifting launch window time indicates a launch into a preferred orbital plane, and it is likely that launch will be right at the opening of the launch window. [end of edit 1] [edit 2] This launch was scrubbed as well, and launch is now slated for 12 January 21:00 UT [end of edit 2]

The launch is in Westward direction, into retrograde orbit. This has led some space news websites to assume that the NROL-47 payload is the 5th TOPAZ (FIA Radar) satellite.

But is it? I have some doubts.

If it is TOPAZ 5, then it is clearly a deviation from the previous four launches. The launch hazard zones from published Maritime Broadcast Warnings show that the launch azimuth is different - previous TOPAZ missions all launched into azimuth 220 degrees, but NROL-47 launches into azimuth 200 degrees, a 20 degree difference.

NROL-47 Launch hazard areas (red) compared to the areas of four TOPAZ (FIA Radar) launches
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This can be clearly seen on the map above, where the NROL-47 hazard zones are in red, and the hazard zones from the four TOPAZ in purple, green, light blue and dark blue. The azimuth and locations of the zones from the four TOPAZ launches are all quite similar, but those of NROL-47 stand out as different.

All the four TOPAZ satellites are in a 123.0 degree inclined retrograde orbit. The NROL-47 launch azimuth results in a retrograde orbit too, but with an orbital inclination of 108.6 degrees, not 123.0 degrees: a 14.4 degree difference.

The orbital altitude aimed for appears to be different too. The four TOPAZ satellites are in 1100 x 1110 km orbits. But the location of the Delta IV Upper Stage de-orbit zone (between South Africa and Antarctica), its shape and the opening time of the window (23:23 UT) points to the NROL-47 payload going into a 1500 km altitude orbit instead.[edit: from the first post-launch radio observations (see update in top of this post), the payload actually appears to be in a ~1100 km orbit, similar to previous TOPAZ: but indeed in a different orbital plane than the previous TOPAZ - end of edit]

estimated trajectory of NROL-47
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So if this is the 5th TOPAZ launching as NROL-47 on Wednesday, then it is going into a quite different orbit compared to the previous four TOPAZ: different in orbital inclination as well as in orbital altitude.

In theory, the Delta IV rocket could do a "dogleg" and (when launching at 20:30 UT) deliver the NROL-47 payload into the 123.0 degree inclined orbit close to the orbital plane of TOPAZ 1 (FIA Radar 1). A second manoeuvre near the south polar pass could then align the RAAN and bring it exactly into the orbital plane of TOPAZ 1.

But why do that, if previous TOPAZ launches simply launched directly into the 123.0 degree inclination orbit?

So in my view, the jury is still out regarding the identity of NROL-47. It could be a 5th TOPAZ but in a quite different orbit compared to the previous four (in itself possible: the Lacrosses also occupied two different orbital inclinations). It could also be something new. If something new, it likely will be a radar satellite (like TOPAZ), given the retrograde character of the orbit. [edit - from radio observations, it appears to be a TOPAZ, but in a different orbital p;lane than the earlier TOPAZ -end of edit]

orbital constellation of TOPAZ 1, 2, 3 and 4 in 123.0 degree inclined orbits
The orbits are spaced 90 degrees in RAAN
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The deliberate re-entry of the Upper Stage happens 1.5 revolutions (2h 55m) after launch.

Estimated search orbits, based on a 108.6 degree orbital inclination, are here. New elset estimates for the new launch date and time are here. South Africa will have two visible passes after launch.

An UPDATE on this post, with post-launch imagery of the payload in orbit, is here.