https://www.nasaspaceflight.com/2017/04/spacex-falcon-9-first-nro-mission-nrol-76/



SpaceX Falcon 9 launches first NRO mission with NROL-76

SpaceX conducted its first dedicated launch for the US National Reconnaissance Office (NRO) on Monday, with a Falcon 9 carrying out the NROL-76 mission. Liftoff from the Kennedy Space Center’s Pad 39A was within a two-hour window, with T-0 occurring at 07:15 Eastern time (11:15 UTC).

SpaceX launch:

Sunday’s initial attempt was scrubbed after a hold was called under one minute to launch due to an “out of family” sensor issue.

The sensor in question was one of the Temperature Ox Tank Outlet (TOTO) sensors on the first stage of the Falcon 9. Data from this sensor was deemed to be an issue, resulting in an engineering meeting at SpaceX HQ in Hawthorne, while allowing the count to proceed while they worked the problem. The decision not to proceed was then passed on to the Launch Control Center in Florida, resulting in the hold and the scrub for the day.

It is understood the sensor was replaced at the pad, with its location in the aft end of the rocket, allowing for another attempt on Monday, which suffered from no issues.

The launch comes a month after SpaceX successfully demonstrated the Falcon 9’s reusability with the successful launch of SES-10 aboard a rocket which featured a “flight-proven” first stage.

Although a newly-built vehicle was used to deploy the National Reconnaissance Office’s NROL-76 payload, SpaceX again attempted to recover the first stage for possible future reuse. This was again successful.

The name NROL-76, shortened from NRO Launch 76, is part of an arbitrary numbering system used to identify the NRO’s satellites – without disclosing their identities – prior to launch.

Once in orbit payloads are usually assigned another numerical designation, prefixed by the letters USA. In recent years, these USA designations have been assigned sequentially, with USA-276 the next available designation in the sequence.

Like most NRO missions, the identity of the satellite – or satellites – that will be deployed during the NROL-76 mission remains classified, as does the mission’s target orbit and the nature of the mission the spacecraft will perform. As is also normal for NRO launches, this has not stopped speculation.

As the launch was the first time a large NRO spacecraft has flown aboard a Falcon 9, it has been difficult to compare NROL-76 to previous launches. SpaceX and the NRO did confirm that after stage separation the first stage would fly back to the Cape Canaveral Air Force Station to attempt a landing at SpaceX’s Landing Zone 1.

Ahead of the launch, notices to airmen (NOTAMs) and mariners have been released, establishing hazard areas that show the course NROL-76 will take after leaving the Kennedy Space Center.

The rocket will head in a north-easterly direction, flying out over the Atlantic Ocean.

This indicates that the payload will be placed into an inclined orbit, and is definitely not bound for geosynchronous orbit. The hazard area off the coast of Florida suggests an orbit inclined at around 50 degrees, although the rocket could perform a dogleg maneuver during second stage flight to increase the inclination.

A second hazard area off the coast of South Africa is likely to be for the deorbit of the second stage – with the NOTAM valid from 14:38 to 17:15 UTC. This suggests either a deorbit burn during the second or third revolution of a low Earth orbit mission, or the first revolution of an intermediate orbit for a spacecraft which would later maneuver into an elliptical Molniya orbit.

The NROL-76 launch was not to be targeting a sun-synchronous orbit, typically used by the NRO’s optical imaging satellites. While it is possible to reach such orbits from the Kennedy Space Center or Cape Canaveral, the rocket would have to perform a series of dogleg maneuvers that would severely limit its payload capacity.

Sun-synchronous launches are instead made from West Coast launch sites such as Vandenberg Air Force Base, where the rocket can fly out over the Pacific without needing to make these maneuvers. Likewise, the mission will not be targeting the retrograde orbit used by the NRO’s Topaz radar imaging satellites, although the prograde orbits used by the agency’s previous-generation Lacrosse and Onyx satellites would be accessible from the East coast.

The NRO operates several fleets of satellites in orbits inclined at around 63 degrees, which can be reached from Cape Canaveral, the Kennedy Space Center or Vandenberg.

These include the Trumpet signals intelligence (SIGINT) satellites and Quasar communications satellites in highly-elliptical Molniya orbits and Intruder naval SIGINT spacecraft in low Earth orbit.

Another use the NRO has had of similarly-inclined orbits was for a pair of stealthy imaging satellites launched under the Misty program.

The first of these, USA-53, was deployed from Space Shuttle Atlantis during the STS-36 mission in February 1990 (Declassified Misty schematic via L2 STS-36). A second, USA-144, was launched by a Titan IV in May 1999, while a third satellite under construction was canceled.

These satellites were highly expensive and far larger than the Falcon 9 would be able to carry to orbit – even in a fully-expendable configuration – and with the apparent cancellation of the Misty program in the mid-2000s it is very unlikely that NROL-76 would be a smaller follow-up satellite.

NROL-76 is unlikely to be an Intruder mission; the NROL-79 launch at the beginning of March deployed two Intruder satellites and, barring the failure of a spacecraft in orbit, the constellation is unlikely to need further replenishment until at least 2020.

In addition, the launch window is not consistent with Intruder; NROL-76 was previously scheduled for mid-April with the same daily launch window, while Intruder launches target specific orbital planes and have launch windows that vary day-to-day. The NROL-76 payload is also probably not part of the Trumpet constellation as these tend to be larger, heavier satellites that would limit Falcon’s ability to return to the launch site, especially if flying a dogleg ascent.

The Quasar constellation was developed to support the NRO’s transition from film-return to electro-optical reconnaissance satellites by providing spacecraft with the ability to transmit images and data back to ground stations without waiting for them to pass overhead.

The first-generation constellation, which launched aboard Titan III(34)B rockets, operated exclusively in Molniya orbits. A geostationary satellite was added along with a second generation of Molniya satellites launched between 1989 and 1996 – the first three aboard the Space Shuttle and the last using a Titan IV(405)A.

Third-generation Quasar launches between 1998 and 2007 replaced the Molniya and geostationary spacecraft, also adding a second geostationary satellite. Further launches between 2011 and 2014 all went to geostationary orbit, replacing satellites launched in 2000 and 2001 and adding a third.

Last year’s NROL-61 mission has been tentatively identified as a fourth-generation Quasar, along with the NROL-52 mission due to launch later this year, indicating further expansion of the geostationary aspect of Quasar.

The Molniya aspect of the constellation has not been replenished since 2007. For a Molniya-orbit constellation to provide continuous coverage it requires three satellites, and both the second and third generation Quasar constellations included three Molniya-orbit satellites.

With the third-youngest Molniya-orbit Quasar the nineteen-year-old USA-137 (NROL-5), this part of the constellation looks to have been discontinued. If the NRO only required two Molniya satellites, however, the USA-179 (NROL-1) spacecraft is not much older than the first two third-generation geostationary satellites were when they were replaced.

A Quasar launch would not necessarily deploy the payload directly into Molniya orbit – Quasars have typically been deployed in a lower initial orbit and maneuvered to their final destinations under their own power.

The last Molniya Quasar launch, NROL-24, used a transfer orbit with a perigee at around 250 kilometers (155 miles, 135 nautical miles) and an apogee at around 16,500 km (10,300 mi, 8,910 nmi) with 60 degrees inclination. Such an orbit would be roughly consistent with the NOTAMs published for second stage reentry, assuming a deorbit burn during the first revolution.

The NRO have announced that the launch “will carry a classified payload designed, built and operated” by the National Reconnaissance Office. This could be an indication that the spacecraft is not part of one of the agency’s existing payload classes, which are believed to be mostly constructed by defense contractors.

This suggests that the payload could either be the first of a new series of satellite or – more likely – a technology demonstration mission. The NRO has occasionally launched spacecraft dedicated to research and development, most recently the Rapid Pathfinder Program (RPP) satellite launched as NROL-66 in February 2011.

The USA-193 satellite, launched as NROL-21 in December 2006, is also believed to have been a technology demonstrator, however, the satellite failed immediately after separating from its Delta II carrier rocket. NROL-76 could be targeting a similar 58.5-degree orbit to NROL-21, however, given the time that has passed it is unlikely that the missions would be related.

NROL-76 was the first NRO mission to launch from the Kennedy Space Center since December 1992, when Space Shuttle Discovery’s STS-53 mission carried a Quasar communications satellite into orbit.

This was the last of seven Space Shuttle missions dedicated to deploying NRO satellites, which began with Discovery’s STS-51-C mission in January 1985.

The need to launch large satellites for the NRO and Department of Defense was a key factor that drove the design of the Shuttle at a time when its reusability was seen as the way forwards for most future space launch activities. The NRO transitioned back to expendable rockets, such as the Titan IV, in the early 1990s.

Screen Shot 2016-09-08 at 14.36.35The Falcon 9’s pad at Launch Complex 39A (LC-39A) was one of two – along with nearby Launch Complex 39B – built to launch Saturn V rockets for NASA’s Apollo program in the 1960s.

Complex 39A supported twelve of the Saturn V’s thirteen launches – including the rocket’s maiden flight, Apollo 4; its first manned flight and the first manned mission to orbit the moon, Apollo 8; all seven missions that attempted a manned landing on the Moon and the deployment of the Skylab space station into Earth orbit.

Following the Skylab launch, which used a modified two-stage Saturn V and marked the rocket’s final flight, Complex 39A was converted to service the Space Shuttle. Columbia began the first Space Shuttle mission, STS-1, from LC-39A in April 1981 and the pad was used for a total of 82 Shuttle launches.

The final Space Shuttle launch from 39A was the Shuttle’s final flight, STS-135, which saw Atlantis lift off on 8 July 2011. SpaceX took over the pad from NASA under a 20-year lease agreed in 2014, with the first launch from the rebuilt pad occurring this February. The launch is the fourth time a Falcon 9 has launched from the Kennedy Space Center.

LC-39A is one of two SpaceX launch pads on Florida’s Space Coast, alongside Space Launch Complex 40 (SLC-40) at the nearby Cape Canaveral Air Force Station. SLC-40 is currently out of action for repairs following the explosion of a Falcon 9 rocket during fuelling ahead of a static fire ground test last September. SpaceX has also leased Cape Canaveral’s former Launch Complex 13, which has been converted into Landing Zone 1, a landing pad for returning Falcon 9 first stages.

The launch was the thirty-third flight of the Falcon 9 and its thirteenth in the current configuration; known as the Falcon 9 v1.2 or Falcon 9 Full Thrust. The Falcon 9 first flew in June 2010, placing a mockup Dragon spacecraft – the Dragon Spacecraft Qualification Unit (DSQU) – into orbit.

The sixth flight, which carried Canada’s CASSIOPE satellite, introduced an improved design – the Falcon 9 v1.1 – which made fifteen launches. The v1.2 configuration, which first flew in December 2015, brought in further enhancements to the design.

The first stage of the Falcon 9 is designed to be reusable. Outfitted with landing gear and grid fins to provide steering as it descends through the atmosphere, the stage is able to make a propulsive landing either on a floating platform – SpaceX’s Autonomous Spaceport Drone Ship (ASDS) – or a ground-based landing pad. SpaceX has successfully recovered the first stage from nine previous Falcon 9 launches; three at Cape Canaveral’s Landing Zone 1 and six at sea.

March’s launch of SES-10, the most recent Falcon 9 mission to date, was the first to re-use a recovered first stage.

Sixty-eight seconds after liftoff, Falcon 9 passed through Max-Q, the area of maximum dynamic pressure or the point in the flight at which the combination of air density and the speed of the vehicle result in it experiencing the greatest aerodynamic loads.

The first stage burned for the first two minutes and seventeen seconds of flight. Its burn ended with main engine cutoff, or MECO.

Payload fairing separation, twenty seconds after the second stage ignites, was the last flight milestone which was announced publicly.

After this, the rocket continued on to orbit in secrecy, with a confirmation of successful spacecraft separation following some time later.

The stage’s final burn began as it approaches the ground, a few seconds ahead of its planned landing. The stage deployed its landing gear and touched down at Landing Zone 1 eight minutes and 46 seconds after lifting off.

The launch was the fifth of the year for SpaceX and the Falcon 9, which has made more orbital launches than any other rocket so far in 2017. Worldwide it was the twenty-third launch of the year.

SpaceX’s next Falcon 9 launch is currently scheduled for no earlier than 15 May, with the Inmarsat-5 F4 spacecraft for British mobile satellite communications operator Inmarsat. The NRO’s next launch is scheduled for 14 August with an Atlas V slated to lift off from Vandenberg Air Force Base on the NROL-42 mission.