Sunday, 1 November 2020

NROL-101: probably a HEO mission [or maybe not! See update at bottom]

click map to enlarge

EDIT 4 Nov 2020 22:30 UT: 

post UPDATED with new maps and new value for inclination parking orbit

EDIT 2, 22:50 UT (Nov 4): the launch has been SCRUBBED for at least 48 hours...

EDIT 3, 7 Nov 22: launch is now currently scheduled for 11 Nov, 22:22 UT 

EDIT 4, Nov 13:  NROL-101 cleared the tower at 22:32 UT (Nov 13)

If weather cooperates,ULA will launch NROL-101, a classified payload for the NRO, on November 11 (postponed from November 3 and 4). Based on Navigational Warnings, the launch window is from 22:00 UT (Nov 11) to 02:45UT (Nov 12), with ULA indicating a launch window start at 22:22 UT. 

[ EDIT: eventually, NROL-101 launched on 13 Nov 2020 at 22:32 UT

The launch is from platform 41 on Cape Canaveral, using an Atlas V rocket in 531 configuration (5-m fairing, 3 strap-on boosters, 1 single engine Centaur upper stage). It would have originally flown in 551 configuration but this was changed. It is the first Atlas V flight to feature the new GEM 63 solid fuel strap-on boosters.

This Navigational Warning has appeared in connection to this launch (updated):

062038Z NOV 20
NAVAREA IV 1074/20(GEN).
   112200Z TO 120245Z NOV, ALTERNATE
   122200Z TO 130245Z AND 132200Z TO 140245Z
   A. 28-38-50N 080-37-34W, 29-58-00N 079-28-00W,
      29-54-00N 079-21-00W, 29-34-00N 079-36-00W,
      29-15-00N 079-45-00W, 28-36-00N 080-23-00W,
      28-30-57N 080-33-15W.
   B. 30-01-00N 079-33-00W, 31-08-00N 078-36-00W,
      30-54-00N 078-14-00W, 29-47-00N 079-11-00W.
   C. 36-38-00N 073-35-00W, 39-03-00N 071-00-00W,
      38-30-00N 070-13-00W, 36-05-00N 072-46-00W.
   D. 51-37-00N 049-45-00W, 53-32-00N 044-58-00W,
      52-54-00N 044-15-00W, 51-03-00N 049-07-00W.
2. CANCEL THIS MSG 140345Z NOV 20.

The launch azimuth from the location of the hazard zones in this Navigational Warning and the initial launch azimuth depicted in a map tweeted by ULA point to an initial lauch into a [value updated] ~56-degree ~57.75 degree inclined orbit:


click map to enlarge

However: this is likely only a temporary parking orbit. The 531 rocket configuration has never been used for a launch into LEO so far, but always for launch into GEO. Given the launch azimuth, NROL-101 will certainly not be launched into GEO. 

So either the payload is destined for LEO but unusually heavy or (more likely) the final orbit aimed for is a HEO orbit (also known as a  Molniya orbit) with inclination ~63 degrees, perigee at ~2000 km over the southern hemisphere and apogee near 37 8000 km over the Arctic. [But: see major update at bottom! It might have been MEO rather than HEO, but this remains uncertain!]

A 63-degree inclined Molniya orbit cannot be reached directly from the Cape, because of overflight restrictions. Hence the initial launch azimuth corresponding to a ~58-degree inclined orbit. If NROL-101 goes into a Molniya orbit, it will do a dog-leg some time after launch, or (more likely) coast in a ~58-degree inclined parking orbit for perhaps several hours before being boosted into a Molniya orbit by the Centaur.

This appears to be underlined by the fact that to date (Sunday Nov 1) no Navigational Warnings have been issued for the reentry area of the Centaur upper stage. This could indicate that the upper stage will be left orbiting in a ~2000 x 37 8000 km transfer orbit, or is disposed into a Heliocentric orbit.

The NRO so far launched three kinds of  satellites into HEO orbits:

1) Data communication satellites (SDS);

2) SIGINT satellites (Trumpet FO);

3) combined SIGINT (Trumpet FO) and SBIRS Early warning satellites.

The last SIGINT/SBIRS combination launched into HEO was USA 278, launched in 2017. The last SDS launch into HEO was USA 198 in 2007 (there was also a launch in 2017 but this was into GEO, not HEO). As Ted Molczan pointed out in  a private com, SIGINT launches into HEO usually were done from Vandenberg, SDS launches from Cape Canaveral. So perhaps NROL-101 will carry a new SDS satellite, but this is far from certain. Radio observations after launch might shed some light on both orbit and payload character.

The initial trajectory will take it over NW Europe some 23 minutes after launch, but in Earth shadow, so the pass will not be visible:

click map to enlarge


UPDATE 15 Nov 2020 15:20 UT

Around 2:30 UT on Nov 14, four hours after launch, sightings of a fuel venting event were observed from the western USA.

This image tweeted by  Marc Leatham shows the V-shaped cloud in Saggitarius, imaged from Joshua Tree National Park:

There is also allsky imagery of the fuel cloud from Taos, New Mexico (look low at the horizon where the milky way touches the horizon(right side), for a 'moving' piece of Milky Way. This is the fuel cloud):

These sightings lead us to believe that the payload perhaps went into the lower part of MEO, not HEO. This is however (emphasis) not certain at this moment.

The launch sequence then could have been insertion into a LEO parking orbit; an apogee raising burn; a perigee raising/circularization burn bringing it into HEO; and fuel vent/orbit separation burn by the Centaur rocket. That latter event caused the observed fuel cloud, at about 8500 km altitude.

ULA reported 'mission successful' around 1:48 UT. For the launch provider, their mission is completed upon payload separation. 1.48 UT corresponds to a pass through the southern apex of the orbit, suggesting payload separation was at that point. This, in combinbation with the observed Centaur vent, would argue against insertion into HEO but does fit insertion into MEO.

If my guess is correct, then this should be the approximate orbit (orbital position is the approximate position for the time of the Joshus Tree fuel cloud sighting):

click to enlarge


Both the Centaur and payload have been catalogued (but without orbital elements) by CSpOC, as #46918 (2020-083A) USA 310 and #46919 (2020-083B) Atlas V Centaur R/B.

If USA 310 indeed went into HEO, then the identity/character of the payload remains a big guess.

Added note, 4 Nov 2020, 21:30 UT: the maps and inclination of the initial parking orbit have been updated based on a map showing the initial trajectory up to fairing jettison tweeted by ULA boss Tory Bruno.

This post benefitted from discussions with Cees Bassa, Scott Tilley, Ted Molczan and Bob Christy.


jim oberg said...

Stage2 fuel dump [?] over North America 2 hr 34 min after launch:

SatTrackCam Leiden said...

Yes, but to be clear: not from this launch. This fuel dump is from the recent GPS Navsat launc, not NROL-101 which at this moment of writing has not been launched yet (launch has again been delayed, to Nov 11)