Photo from ULA of NROL-61 ready to launch. The Sun is rising. What did I promise Tory to do?
Mission Rundown: ULA - Atlas V 421 - NROL-61
Written: December 31, 2022
Firing with one or two barrels?
United Launch Alliance successfully launched one or ‘two’ satellites for the US National Reconnaissance Office Thursday aboard an Atlas V rocket.
Liftoff for the mission designated NRO Launch 61, or NROL-61, occurred from Cape Canaveral’s Space Launch Complex 41 - SLC-41 at the start of the launch window that opened at 08:37 local time (12:37 UTC).
Thursday’s mission was United Launch Alliance’s (ULA) twenty-third in support of the National Reconnaissance Office – as well as the thirteenth Atlas V launch for the agency.
The National Reconnaissance Office (NRO) is responsible for the fleet of satellites used by US intelligence agencies for surveillance, as well as in supporting roles such as research and development or communications.
With the exception of a few demonstration missions, details of the NRO’s spacecraft and operations are kept classified, with spacecraft only being identified publicly by means of their launch number and a public designation assigned after launch consisting of the letters USA, followed by a number.
Since 2007 the USA designations have been assigned sequentially, so once in orbit, the single satellite payload of Sunday’s launch is expected to become USA-269.
The NROL-61 Payload
NROL-61 could be a fourth-generation Quasar; the use of a larger rocket to deploy it would suggest a larger and more powerful spacecraft than its predecessors.
Quasar, also known as the Satellite Data System, is a constellation of communications satellites operated by the NRO to support its other intelligence-gathering activities; relaying data from other satellites to the ground in real-time, without having to wait for the intelligence-gathering satellites to pass over ground stations on friendly territory.
Thursday’s launch was the sixth flight of an Atlas V 421 and the fifth to geostationary transfer orbit. The previous geostationary satellites launched by this configuration were two Wideband Global Satcom spacecraft, which used Extended Payload Fairings, and the commercial ICO G1 and Morelos 3 communications satellites which both used the Extra-Extended fairing.
The ICO satellite, since renamed EchoStar G1, was based on Space Systems Loral’s LS-1300 bus, while Morelos – also known as MEXSAT-2 – was based on Boeing’s BSS-702HP-GEM bus. Both carried large reflector antennas to facilitate communications via mobile communication devices. It is, therefore, possible that a fourth-generation Quasar may carry a similar antenna.
An alternative explanation would be that the fourth-generation satellites are smaller than their predecessors, but will now launch in pairs. NRO budget documents published by the Washington Post in 2013 show combined line items for Quasars 17 and 18, 20 and 21 and 22 and 23, while Quasar 19 was procured separately and may have been the satellite launched in 2014, with 17 and 18 having previously launched separately.
It is possible that two Quasars could be among the three contracts awarded by the US Government to Boeing in early 2013 for BSS-702SP satellites, a modified version of the Boeing 702 platform optimized for dual launch, to be launched together by a single Atlas.
SpaceX has already conducted two dual-launch missions of BSS-702SP satellites for commercial operators Eutelsat and Asia Broadcast Satellite using its Falcon 9 rocket.
NRO could have asked ULA to prepare a launch vehicle capable of launching two Quasar satellites based on the Boeing platform BSS-702SP optimized for dual launch.
The Atlas V 421 Launch
Following a nominal countdown, the Common Core Booster’s RD-180 main engine ignited at the 2.7-second mark in the countdown, reaching liftoff thrust at zero.
Ignition of the solid rocket motors and liftoff of the vehicle occurred 1.1 seconds later, with the Atlas departing from Cape Canaveral’s SLC-41 and ascending towards orbit.
A few seconds into flight the Atlas V rocket began maneuvers to attain its planned launch trajectory, with an azimuth of 99 degrees taking it Eastward over the Atlantic Ocean.
AV-065 reached Mach 1, the speed of sound, 47 seconds into its flight, passing through the area of maximum dynamic pressure, or Max-Q, five seconds later. A little over ninety seconds after liftoff the solid motors burnt out; however, these remained attached until 129 seconds mission elapsed time.
1st stage flight ended with Booster Engine Cut-Off, or BECO, 4 minutes and 10 seconds after launch; the Common Core Booster engine having depleted its propellant.
The spent stage was jettisoned six seconds later, with ignition of the Centaur’s RL10C-1 engine occurring ten seconds later.
The final event before the mission entered a news blackout was the separation of the payload fairing at four minutes and thirty-four seconds after liftoff.
Third-generation Quasar satellites were launched into low-perigee geostationary transfer orbits; assuming NROL-61 targeted a similar orbit this would have called for two burns of the Centaur’s engine prior to spacecraft separation.
The first of these would have lasted around eleven minutes, followed by a ten-minute coast and a four-minute second burn. An alternative profile, to achieve a higher-perigee orbit, would call for a longer first burn and shorter second burn, separated by a coast phase of more than ninety minutes.
ULA did release the confirmation the mission was successful.
A hazard warning announced for the Pacific Ocean between 20:59 and 22:00 UTC suggests the Centaur will be deorbited at the end of its mission, eight or nine hours after an on-time liftoff. It will crash land about 750 km south of Hawaii.
This suggests that the stage will complete one revolution in geostationary transfer orbit, with a deorbit burn following spacecraft separation.
Ted Molczan, a leading member of the amateur satellite observing community, speculated that from the orientation of the disposal hazard area that the Centaur second stage is likely to perform a maneuver that will reduce the orbital inclination of the deployment orbit to around 13.4 degrees from its original 28.5 degrees.
The Centaur second stage will perform an orbit insertion burn, a geostationary transfer orbit burn and a short deorbit burn lowering the perigee of the transfer orbit to a low or negative number. Aiming below the Karmen 100 km line or Earth surface will suffice.
Both the payload, cataloged as USA 269 [41724/16047A], and the Centaur upper stage were observed from Australia shortly after the Centaur deorbit burn.
USA 269 was in a 843 km x 35739 km x 18.9 degree orbit
Centaur had a terminal -252 km x 28014 km x 18.9 degree orbit
If the 3rd burn is a geostationary insertion burn using all of the Centaur propellant reserves then it won’t come back to Earth and remain in a graveyard orbit below the geostationary orbit. It will use the blowout valves to depressurize itself while breaking its orbit speed just enough to avoid colliding with other space vehicles or derelict space debris.
The Atlas V 421 rocket
The Atlas V that carried out the NROL-61 mission had the tail number AV-065.
Its 421 configuration is that the vehicle consists of a single Common Core Booster (CCB) first stage augmented at liftoff by two Aerojet AJ-60A solid rocket motors, a single-engine Centaur upper stage and a four-meter - 13 foot payload fairing to encapsulate the NROL-61 spacecraft, protecting the payload during the ascent through Earth’s atmosphere.
The spacecraft itself was encapsulated within an Extra-Extended Payload Fairing (XEPF) – at 14 meter (46 feet) in height the tallest of three available four-meter (13-foot) diameter fairings – which has also never before been used for an NRO mission.
Atlas V 421 split in its major parts. Known details about Atlas V and Centaur are noted
Ted Molczan states in his analysis of the performance of the Atlas V 421 that it could deliver about 590 kg more to a 13.4 degree inclination GTO than the 401 to a 20.7 degree GTO, which tends to support the hypothesis that the spacecraft is a new model.
Another clue is the use of a longer payload fairing than one NROL-33 and NROL-38 used, as reported by Spaceflight Now.
Reducing the GTO inclination from 20.7 deg to 13.4 deg would reduce the payload's delta-V to reach the expected approximately 4.9 deg inclined GEO orbit by about 122 m/s.
This would reduce the payload's fuel expenditure to reach GEO, enabling a greater mass to reach GEO, resulting in some combination of greater payload mass and greater fuel mass for station-keeping and other orbit maneuvers.
The latter would tend to increase the useful life of the spacecraft.
Ted Molczan analysis of the data in the Atlas V Launch Services User's Guide, Revision 11, Table 2.6.2-1: Atlas V 401-431 Geo-transfer Orbit Performance, revealed the following relevant performance data.
Atlas V 401 - 20.7 inclination degree - maximum payload ~ 4324 kg ± 100 kg
Atlas V 411 - 13.4 inclination degree - maximum payload ~ 4205 kg ± 100 kg
Atlas V 421 - 13.4 inclination degree - maximum payload ~ 4914 kg ± 100 kg
NROL-61 payload is with this information set at 4900 kg until other data is found.
Facts on the Atlas V 421 launch vehicle
Height of Atlas V 421: 194 feet (59.1 meters)
Fuel onboard: 91,000 gallons of liquid propellant
First stage Atlas: 25,000 gallon RP-1 - 48,800 gallon LOX
Second Stage Centaur: 13,050 gallon LH2 - 4,150 gallon LOX
LOX+LH2 = 66,000 gallon of cryogenic liquid propellant in three tanks
150 kg (340 lb) of Hydrazine - N2H4 is stored in a pair of bladder tanks
Helium - He pressure vessel storage tanks: Unknown so far
Nitrogen - N2 pressure vessel storage tanks: Unknown so far
2 GEM-63 SRB: 200,000 pounds of solid fuel
Mass at liftoff: 969,500 pounds (439,758 kg)
Thrust at liftoff: 1.6 million pounds (7.1 mega-Newtons)
A: Geosynchronous Transfer Orbit - 3,243 x 22,000 miles (834 x 35,739 km x 18.9 deg)
B: Geosynchronous Transfer Orbit - 3,243 x 22,000 miles (5,218 x 35,500 km x 17.6 deg)
Flight plan A includes a 58 second deorbit burn. Centaur second stage is scuttled.
Flight plan B includes a 58 second perigee raise burn. Centaur is derelict space debris.
