Saturday 29 April 2017

What is NROL-76 and what orbit wil it be launched into?

Tomorrow, 30 April 2017, with (from the area warnings) a three-hour launch window starting at 10:55 UT, SpaceX will launch a classified satellite for the NRO. The launch is designated NROL-76 and will happen from launchpad 39A at Cape Canaveral, Florida. The press-kit is here.

There has been some speculation on what this launch might be and what orbit it will go into.

Considering the latter, Ted Molczan discussed three options in two separate SeeSat-L posts (here and here): a launch into HEO (Molniya) orbit of a new SDS satellite; a launch into GEO of a new NEMESIS; or a launch into LEO, perhaps a new version of the ill-fated USA 193 launch from 2006.

The launch azimuth deduced from the Area Warnings that appeared after Ted posted his initial speculation on the payload, narrowed the options down to two: HEO or LEO. To me, the Area Warnings strongly suggest the second option: a launch into LEO, perhaps a USA 193 follow-up.

The Maritime Area Warnings published for the launch show two hazard zones: one near Cape Canaveral, and one, with a window opening four-and-a-half hours later than the launch window, in the Indian Ocean stretching from south of Madagascar to north of Kerguelen:

NAVAREA IV 342/17 [1 of 1][[WWNWSFOLDER]]

ALTERNATE 011055Z TO 011354Z MAY
28-39N 080-39W, 30-34N 078-45W,
31-32N 077-34W, 31-26N 077-13W,
31-06N 077-11W, 30-47N 077-32W,
30-08N 078-26W, 28-29N 080-21W,
28-26N 080-27W, 28-25N 080-35W,
28-25N 080-38W.
2. CANCEL THIS MSG 011454Z MAY 17.//

Authority: EASTERN RANGE 211830Z APR 17.

Date: 271553Z APR 17
Cancel: 01145400 May 17

HYDROPAC 1447/17 [1 of 1][[WWNWSFOLDER]]

DNC 02, DNC 03.
ALTERNATE 011438Z TO 011715Z MAY
30-31S 038-04E, 30-40S 040-19E,
40-11S 060-06E, 47-31S 080-01E,
48-56S 079-46E, 49-00S 075-21E,
47-12S 063-50E, 41-51S 049-33E,
35-39S 040-15E, 32-07S 037-37E.
2. CANCEL THIS MSG 011815Z MAY 17.//

Authority: EASTERN RANGE 211827Z APR 17.

Date: 250231Z APR 17
Cancel: 01181500 May 17

I have put them in maps for your convenience:
click map to enlarge
The first area points to a launch azimuth of 43-45 degrees, indicating (if no dog-leg is involved) launch into an orbital inclination of 50-51 degrees as can be seen in the first map I prepared, above. This would at first sight exclude launch into HEO/Molniya orbit at inclination 63.4 degrees, unless of course a dog-leg manoeuvre is involved, which is possible.
click map to enlarge

The second area, in the Indian Ocean, points to the de-orbit of the upper stage about 4.5 hours after launch and actually matches a launch into an ~51 degree inclined LEO orbit as well.

In the map below, I have printed an estimated Low Earth orbit for the upper stage of the launch, based on the 2006 USA 193 orbit in terms of apogee and perigee, but with the orbital inclination changed to 51 degrees. About 2.4 orbits after launch, near 14:38 UT when the hazard warning window opens, the stage would be over Africa on its way to the hazard area, which has a position and curvature matching the trajectory (given the uncertainties in my orbit estimate) close enough, in my opinion, to accept this potential scenario of launch into an approximately 51 degree inclined, about 355 x 375 km orbit, or something similar to that:

click map to enlarge

One has to wonder though why the de-orbit is 2.5 revolutions after launch, and not simply during the second part of the first revolution. Perhaps some experiments will be done with the stage? Or does it deliver additional (small) payloads perhaps? Your guess is as good as mine.

In terms of the payload itself, Ted Molczan has posted some interesting info to SeeSat-L suggesting the payload is based on  Boeing's commercial, completely electrical thrust BSS-702SP bus.

The purpose of the payload(s?) is completely unclear at the moment. Radar satellites such as Lacrosse/ONYX were previously launched into 57-58 degree inclined orbits or their retrograde 123 degree equivalent (FIA/TOPAZ). Optical reconnaissance satellites such as KH-11 are launched in 97 degree inclined sun-synchronous orbits. NOSS (INTRUDER) SIGINT duo's are launched into 63.4 degree inclined stable perigee orbits. If this payload ends up in a 51 degree orbit, this is new.

There is a possibility that, while initially launched and inserted into a 51 degree orbit (a launch trajectory with which SpaceX is familiar from their CRS launches to the ISS), the payload next manoeuvres into a 58 degree or even 63.4 degree orbit on its own, using its electrical thrusters.

It will be interesting to see what orbit the object or objects eventually will be found in. It is likely it will be designated "USA 276".

If the 51-degree orbital inclination scenario is correct, observers in the Northern hemisphere will, unfortunately for me, not have visual sighting opportunities after launch: optical detection will rest on the shoulders of Southern hemisphere observers.

[added note 29 apr 15:15 UT] On April 30, be aware for possible re-entry sightings from Madagascar, especially the southern part of the island, near 14:40 UT, in early twilight (assuming launch at ~11:00 UT).

Wednesday 5 April 2017

VIDEO: the ISS Fabric Shield (again), and North Korea's Kwangmyongsong-4

Yesterday I posted April 3 photographic imagery of the ISS Fabric Shield (1998-067 LF), a 1.5 x 0.6 meter anti-micrometeoroid shield astronauts inadvertently let fly into space during an EVA on March 30 (see my previous post for more details).

Yesterday evening April 4, in late twilight, I managed to film the object, which was now 1m 45s ahead of the ISS. The video, shot with a WATEC 902H low-light-level camera and a Samyang 1.4/85 mm lens, is above.

Later in the evening I also targetted  North Korea's Kwangmyongsong-4 (KMS-4, 2016-009A) which I had filmed, but as a very faint object, a week before as well. This time, KMS-4 was much brighter due to a more favourable illumination angle, and is easy to see as it cruises past Alcor and Mizar:

Both the ISS Fabric Shield and KMS-4 do not show a clear periodic brightness variation in the video imagery. The only variation that is there are slow trends (altitude and illumination angle related) and fluctuations within the fluctuation expected from atmospheric scintillationand oscillations in the video signal (estimated by looking at variations in the apparent brightness of a comparison star) :

click diagram to enlarge

Monday 3 April 2017

The ISS Fabric Shield accidentally released from the ISS imaged in orbit

On March 30, 2017, NASA astronauts Shane Kimbrough and Peggy Whitson conducted an EVA from the International Space Station to prepare a new docking port and install new equipment on the outside of the ISS.

click to enlarge

During this spacewalk, they accidentally released a 1.5 x 0.6 meter large protective Fabric Shield, a shield against micrometeoroids that was one of four to have been installed that day on one of Tranqility module's ports. Somehow it got loose  and floated away in space, before the astronauts were able to retrieve it. Oopsy!

Once floating free in space, and having become space debris, it was catalogued by JSpOC as object nr. 42434, 1998-067LF.

The image above shows the shield, imaged from Leiden last night during a zenith pass with an 1.4/85 mm lens. It is faint and was almost exactly a minute in front of the ISS. It seemed steady in brightness on the 3 images I obtained (spanning an arc of 15 seconds in time).

Here is a screencap of the moment the object floated away during the EVA, somehow having come loose of its tether:

click to enlarge

The image below shows the ISS, a minute later (bright stars are kappa and iota UMa):

The accidentally released Fabric Shield has a relatively large surface relative to its weight [added edit: it weights 8 kg and measures 1.5 x 0.6 meter], which means it will quickly decay and re-enter, probably within 5 to 6 months from now.