Atlas V successfully launches NROL-101

by William Graham

United Launch Alliance’s Atlas V rocket carried a National Reconnaissance Office satellite to orbit Friday in a launch that marked a major milestone for the next-generation Vulcan rocket as Atlas V debuted the new GEM-63 solid rocket boosters from Northrop Grumman — the start of a switch away from the Aerojet Rocketdyne boosters.

Liftoff is set from Florida’s Cape Canaveral Air Force Station and SLC-41 at 17:32 Eastern Standard Time (22:32 UTC) on Friday, 13 November.
(Lead Photo by Brady Kenniston for NSF)

The first launch attempt on 4 November was placed into an unplanned hold at the T-1 hour 47 minute mark after an issue with a ground-side valve in the liquid oxygen farm at the pad malfunctioned, forcing a stop to fueling operations.

After attempts to troubleshoot and resolve the issue by sending a pad re-entry team to the site, the launch was scrubbed.  At first a two day delay, then a four day push to fix the issue, Tropical Storm/Hurricane Eta then pushed the launch to Friday, 13 November.

This launch carried out the NRO Launch 101 (NROL-101) mission for the National Reconnaissance Office (NRO), placing into orbit a clandestine national security payload. The launch marked the new GEM-63 solid rocket motor’s debut – with three of these boosters augmenting Atlas V’s first stage.

This represents a cost-saving for Atlas V missions over the AJ-60A motors used on previous launches and allows the GEM-63 to be proven in flight before the use of stretched GEM-63XL motors on ULA’s new Vulcan rocket that is slated to fly next year.

The NRO is one of the United States’ main intelligence agencies and is tasked with operating and maintaining the nation’s fleet of spy satellites, with its spacecraft designed to gather electronic and photographic reconnaissance data directly, or to support intelligence gathering through other means – such as with communications relays. While details of most of its spacecraft and its operations are highly classified, past leaks and observation of the satellites in orbit have revealed many details of the types of satellite operated and how they can collect data.

Hazard areas published in advance of the launch show that Atlas V would follow a northeasterly track after departing Cape Canaveral, meaning that NROL-101 is likely targeting an inclined – but not polar – orbit. The NRO already operates several types of satellite in inclined orbits – including Trumpet signals intelligence satellites and Quasar communications spacecraft in elliptical Molniya orbits and Intruder ocean surveillance spacecraft in low Earth orbits – all at inclinations of around 63.4 degrees.

The agency also has surviving Onyx radar-imaging spacecraft in 57 and 68-degree orbits; however, these have been superseded by later Topaz spacecraft operating in retrograde orbits. Historically the agency operated the stealthy Misty imaging satellites in approximately 65 degree orbits, although the last of these satellites was launched over 20 years ago it is unlikely to remain in service.

The version of Atlas V was the 531 configuration, which can theoretically carry a maximum payload to low Earth orbit of 15,500 kilograms (34,000 lb). At the rocket’s nose, the payload is encapsulated in a 5-meter payload fairing (the actual diameter is 5.4 meters, or 17.7 feet) measuring 23.4 meters in length.

This is the medium option of the three, 5-meter fairings available for Atlas V and has to date only been used to carry satellites with large, furled antennae which would not fit into the shorter option used for most flights. The longest fairing size has never been flown.

No previous NRO missions have used the 531 configuration of Atlas V. However, the agency’s Topaz radar-imaging satellites are one of the two classes of spacecraft to have previously used the medium-length fairing – the other being the US Navy’s MUOS communications satellites. But NROL-101 is unlikely to be a Topaz spacecraft. These operate in retrograde orbits that could not easily be reached from Cape Canaveral. And the spacecraft are not heavy enough to require equipping the Atlas V with solid rocket boosters… while this mission has three.

A heavier successor satellite, operating in either the 57 or 68 degree plane used by the previous-generation Onyx satellites, cannot be discounted. Another remote possibility is a follow-up to Misty; however, this program’s original satellites were far larger than anything the Atlas V would be able to carry.

The Atlas V fairing for this mission – photo: Stephen Marr for NSF

One possible identity for the NROL-101 payload is a pair of Intruder satellites. This program, which is also known as the Naval Ocean Surveillance System (NOSS) uses four twin-satellite formations in low Earth orbit to pinpoint ships at sea based on their radio transmissions. Each pair of satellites has been launched together aboard a single rocket, with the system currently believed to be in its third generation. These satellites are replaced after about 10 years, with the oldest of the four primary sets of satellites currently nine and a half years old – and therefore due for replacement early next year.

Previous Intruder launches were at the upper end of what the Atlas V could carry with no solid rocket boosters – although one launch flew with a single booster in order to make a more direct insertion into orbit after the previous launch encountered a problem during a lengthy coast phase. Both satellites could also fit within a four-meter Extended Payload Fairing (EPF), meaning that if NROL-101 is an Intruder mission, it must represent the start of a new fourth-generation system. These new satellites would either be larger and heavier than the third-generation vehicles or designed to operate in groups of three rather than two.

A trio of NOSS satellites would not be unprecedented: in its first and second generations, the constellation used groups of three satellites, nicknamed “Triads”. These were launched along with a fourth satellite, an active deployment mechanism, which maneuvered and released the satellites into their final orbits before either ceasing operations or going on to perform its own independent mission.

If the launch does carry an Intruder payload, the slightly earlier-than-expected launch date could allow for additional on-orbit testing of the new-generation satellites. The NROL-85 mission – expected to fly aboard a Falcon 9 rocket in the third or fourth quarter of next year – is already known to be an Intruder mission, its target orbit having been published as part of a tender for launch services in 2017. This would be slightly later than expected to replace the oldest pair of NOSS satellites, USA-229, so it could instead represent an earlier replacement of the second-oldest pair of satellites if NROL-101 replaces the older pair.

Another possible destination for NROL-101 is Molniya orbit. The two Trumpet satellites that operate here eavesdropping on foreign radio signals have been replaced in the last few years. These satellites are likely smaller and heavier than NROL-101 since their carrier rockets featured shorter payload fairings and more solid rocket boosters. Meanwhile, the Quasar communications satellites – used to relay signals from other NRO spacecraft – have not been upgraded for many years. These are one part of the Quasar network – also known as the Satellite Data System (SDS) – operating alongside satellites in equatorial geostationary orbits to provide coverage at high latitudes where establishing a link via geostationary orbit may prove difficult.

With no Quasar satellites having launched to Molniya orbit since 2007, despite the subsequent replacement and expansion of the geostationary network, it has been speculated that this part of the constellation had been discontinued. This is backed up by the fact that if the NRO means to keep three satellites operational for continuous coverage, the nearly 23-year-old USA-137 satellite would need to still be in frontline service. While it is reasonable to expect that Molniya-orbit satellites may use their propellant reserves more slowly than their geostationary counterparts – and therefore not see their lives as constrained by this factor – and some spacecraft can achieve incredibly long terms of service, intentionally leaving such an old spacecraft in a critical role seems unlikely.

If NROL-101 is carrying a Quasar payload, it is unlikely to be a single satellite of the same configuration as the most recent geostationary missions, as these fit within a 4-meter payload fairing and the Atlas rockets that carried them only required two boosters. A single large satellite with a MUOS-style dish for mobile terminal communications is possible, or alternatively the mission may include multiple satellites.

The US government ordered three spacecraft from Boeing in 2013 for an undisclosed agency and mission, based around the BSS-702SP platform. BSS-702SP satellites can be launched individually or in pairs without the need for additional hardware and are in service with several commercial communications providers.

The length of time since the last Quasar launch – NROL-24 in December 2007 – is harder to explain. However, this could be down to delays in payload development or the reversal of an earlier decision not to replace these satellites. It is also possible that NROL-101 could be a new type of satellite – for example: a new type of signals intelligence satellite with a large receiver antenna, to complement the existing Trumpet spacecraft or a completely new type of mission.

Once NROL-101 reaches orbit, more details should become apparent as amateur skywatchers around the world will observe the spacecraft and report on the orbit it has entered, whether more than one satellite has been deployed, and any radio signals or emissions that might be detected.

The mission patch for the NROL-101 launch features the Earth – with the Middle East in the center – on a background of stars, four of which are more pronounced than the others. Four points appear from behind the Earth at right angles, while a gold band stretches around the outside of the patch. The NRO has described this as being inspired by J. R. R. Tolkien’s Lord of the Rings novels, with the gold band representing the “one ring” and the inscription on the patch reading “Goodness Persists” in the fictional Elvish language from the series.

NRO patches occasionally include subtle clues or in-jokes that can give away details about the mission. However, this practice has become less common as it became more widely known over the last 15 to 20 years. The four points appearing from behind the Earth could allude to compass points that have appeared on previous patches from Intruder missions, or the points of a larger star that has been seen on Quasar patches.

Along with the four larger stars, this could indicate some significance to the number four for this mission – either that there are four satellites aboard the rocket, it is the fourth satellite in a series or part of a group of four satellites, or that it is part of the fourth generation of satellites for a particular project.

The designation NROL-101, or National Reconnaissance Office Launch 101, is part of a series of pseudo-randomly assigned designations used to identify NRO satellites prior to reaching orbit. Once deployed, the satellite will be redesignated with a USA number, the system of sequential designations used to identify most American military spacecraft once in operation.

Prior to the first scrubbed launch attempt, NROL-101 had been expected to assigned the designation USA-309; however, with the launch slipping, this designation was instead given to the GPS III-04 satellite.  The next designation in the sequence, which will now likely belong to NROL-101, is USA-310.

The Atlas rocket that carried the NROL-101 payload into orbit had tail number AV-090. It was the 86th mission for United Launch Alliance’s workhorse Atlas V rocket and the fourth to use the 531 configuration. This launch marked the first time that Atlas will fly with Northrop Grumman’s GEM-63 solid rocket boosters instead of the Aerojet Rocketdyne AJ-60A motors used on earlier missions.

Designed to mimic the AJ-60A as closely as possible in terms of both size and performance, the GEM-63 builds on the wealth of experience with solid motor design that Northrop Grumman inherited through its 2018 purchase of Orbital ATK, itself originating from a string of mergers including companies such as Orbital Sciences Corporation, Alliant Techsystems and Thiokol. The company’s Graphite Epoxy Motor (GEM) series of boosters was originally developed for the Delta II rocket, being introduced with the 7000-series configurations in November 1990.

In addition to the Delta II, GEM boosters were also used on the short-lived Delta III rocket – with the enlarged GEM-46 boosters later retrofitted to the Delta II to make a Delta II Heavy vehicle with increased payload capacity. The Medium+ configurations of the Delta IV used GEM-60 motors.

The name Graphite Epoxy Motor comes from the carbon epoxy composite used in the construction of its casing, making the GEM-40 – as the original version was named – significantly lighter than the steel-cased Castor boosters that had been used on earlier Delta rockets. The number in the motor’s designation gives its diameter in inches – so the original GEM-40 measured 40 inches, or 102 centimeters, across, while the GEM-63 for Atlas V has a diameter of 63 inches, or 160 centimeters. Each booster is filled with QDL-4, a propellant compound based on hydroxyl-terminated polybutadiene (HTPB).

In total, 1,152 Graphite Epoxy Motors have flown before this launch as part of 162 individual rockets. Over these missions the GEMs have demonstrated very good reliability, with only three mission-affecting in-flight anomalies related to the boosters. Most notable was the loss of Delta 241, a Delta II rocket with the GPS IIR-1 satellite aboard in January 1997. One of the GEM-40 boosters sustained microscopic damage before launch, resulting in a crack opening up in its casing as the rocket began to ascend. Within 12 seconds of liftoff, the booster disintegrated, with the rocket’s flight termination system activating to destroy the rest of the vehicle. Conversely, the Mugunghwa 1 or Koreasat 1 satellite mission, an earlier Delta II flight reached a lower-than-planned orbit after one of its GEM-40s failed to separate.

The third anomaly occurred during the Delta III rocket’s first flight in August 1998, which was destroyed by range safety after its GEM-46 motors ran out of hydraulic fluid and the vehicle lost attitude control. In this case, the failure was attributed to a problem with the rocket’s flight control system – which had been designed using data from earlier Delta II launches and did not account for the different oscillations induced by the larger vehicle – rather than a malfunction in the boosters themselves.

For its part, the AJ-60A has flown on 40 previous Atlas V missions – the rocket’s other 45 launches having used the 401 and 501 configurations with no solid rocket boosters – with a total of 127 boosters flown and a perfect reliability record. The decision to replace the AJ-60A with the GEM-63 was driven by both its lower cost and the opportunity to prove the hardware in flight conditions before ULA’s next-generation Vulcan rocket comes onto the scene. Vulcan will use up to six stretched GEM-63XL boosters depending on its mission requirements.

GEM-63 during testing – via NG Systems

Due to the care that Northrop Grumman has taken in matching the dimensions and performance characteristics of the AJ-60A boosters, the GEM-63 is seen as a “drop-in” replacement with no significant changes required to Atlas V, the mission profile, or its supporting infrastructure to accommodate the boosters.

ULA plans to fly out their remaining stock of AJ-60A motors on upcoming launches, gradually transitioning to the GEM-63s. The most recent plan – as stated by ULA to NASASpaceflight – is to fly out the AJ-60A stock on a few, but not all, missions in 2021 before transition Atlas V completely to the GEM-63s by 2022.

Atlas V itself was developed as part of the US Air Force’s Evolved Expendable Launch Vehicle (EELV) program – now known as National Security Space Launch (NSSL). First flying in 2002, Atlas V boasts a near-perfect success record with its only blip being a partial failure in 2007, when a fuel leak on the upper stage led to a pair of National Reconnaissance Office Intruder satellites, the NROL-30 mission, being delivered to a lower-than-planned orbit. Despite this, the NROL-30 spacecraft were able to correct their own orbits and appeared to enjoy a nominal-duration mission.

Atlas V is a two-stage rocket consisting of a Common Core Booster (CCB) first stage and a Centaur upper stage. Designed to fly in multiple configurations to adapt to differing payload requirements, each Atlas V model has a three-digit identification number, which indicates the diameter of its payload fairing, number of solid rocket motors attached to the first stage, and the number of engines on its upper stage. In the case of the 531 configuration, which will be used for this launch, this means a 5-meter fairing, three GEM-63 boosters, and a single-engine Centaur upper stage.

The launch took place from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station. This pad is used for all Atlas V launches from the East Coast, with a second launch pad available at Vandenberg Air Force Base on the West Coast for missions requiring high-inclination orbits.

SLC-41 was originally built for the Titan IIIC rocket, as part of the Integrate-Transfer-Launch complex along with nearby SLC-40 and a shared vertical integration building. Complex 41 served the Titan family of rockets until 1999 before being turned over to Atlas. Following modifications, including the demolition of the Titan-era fixed and mobile service towers, the pad was ready to support Atlas V’s maiden flight in 2002.

Atlas V on SLC-41 – photo by Thomas Burghardt for NSF

Final assembly of the Atlas V rocket took place in the Vertical Integration Facility (VIF), about 550 meters (1,800 feet) away from the launch pad. With the launch scheduled for Wednesday, Atlas was rolled to the launch pad on Monday, but returned to the VIF later the same day after concerns that high winds at the launch pad may have damaged an environmental control system (ECS) duct on the fairing. Atlas returned to the launch pad atop its mobile launch platform on Wednesday morning, ready for Wednesday’s scrubbed launch attempt.

At the end of the countdown, following checkout and fuelling of the rocket, Atlas’ RD-180 main engine ignited at T-2.7-seconds to begin the NROL-101 mission. About 3.8 seconds later, the GEM-63 motors ignited and AV-090 lifted off from Cape Canaveral for the journey into orbit. Just over 5.5 seconds into the flight, Atlas performed a pitch and yaw maneuver to establish its initial north-easterly launch azimuth. Later in the ascent, the rocket had the option of a dog-leg maneuver to change its trajectory, allowing a higher-inclination orbit to be reached without overflying land too early in the climb to orbit.

Under the power of its RD-180 engine, which burns RP-1 kerosene propellant and liquid oxygen, and the three GEM-63 strap-ons, Atlas accelerated quickly. At 38.8 seconds after liftoff, the rocket reached Mach 1, the speed of sound, and begin supersonic flight. The area of maximum dynamic pressure, where the rocket experiences its highest aerodynamic loads, came about 12.5 seconds later.

The GEM-63 boosters are designed to burn for 97.6 seconds. After depleting their propellant, the spent casings are kept attached to the rocket until a point in the flight where they can be released without any danger of recontact between them and the first stage. Jettison occurred about 16.3 seconds after burnout, at 1 minute 53.9 seconds mission elapsed time.

Once Atlas reaches space, it shed its payload fairing. The fairing serves to protect the NROL-101 payload and the rocket’s Centaur upper stage during the ride through Earth’s atmosphere. It is no longer required in the vacuum of space and separates to reduce weight and clear a path for the upper stage to separate from the first when the time comes. Fairing separation occurred 3 minutes 19.3 seconds after liftoff, with the forward load reactor – a device attached at the top of the Centaur stage to help spread the payload’s weight across the lower part of the fairing – followed suit a few seconds later.

After fairing separation, the launch entered a media blackout. This is normal for secretive US national security missions, where the target orbit remains officially classified – even if observers can easily determine it after launch. Although details of flight events have not been disclosed during this period, the early stages of flight will be similar to previous launches. After fairing separation, the RD-180 engine can be expected to continue firing for about another minute, before the mission reaches Booster Engine Cutoff, or BECO, when the first stage shuts down having completed its role in the ascent.

About 6 seconds after BECO, the two stages of the Atlas V rocket will separate from each other, with the Centaur upper stage entering its pre-start sequence. Centaur ignition will come about 10 seconds after separation. The stage’s RL10C-1 engine will ignite for the first of potentially several burns, depending on the target orbit and the mission profile that will get it there. For a launch to low Earth orbit – for example, with an Intruder payload – Centaur might make either a single longer burn for a direct insertion or an initial burn to reach a lower parking or transfer orbit followed by a coast and another burn to circularise the trajectory. A launch to a higher Molniya orbit would require a two-burn profile. In contrast, more unlikely orbits – such as a circular medium Earth orbit – might call for one or two burns to reach a transfer orbit followed by a lengthy coast phase and a final circularisation burn.

This launch was the fifth and final Atlas V mission of 2020, following successful launches in February with the Solar Orbiter mission, March with the AEHF-6 communications satellite for the US Air Force, May with an X-37B Orbital Test Vehicle, and July with the Perseverance rover and Ingenuity rotorcraft bound for Mars. At the beginning of January, the next Atlas launch is currently expected to carry the OFT-2 mission, a repeat uncrewed test flight for Boeing’s Starliner spacecraft.

Before this, ULA has two Delta IV Heavy launches scheduled for the end of this year: the NROL-44 mission from Cape Canaveral, which is currently awaiting a new launch date following several delays since its first launch attempts in August, and NROL-82 from Vandenberg in December.

The two Delta IV launches and its NROL-108 mission on a SpaceX Falcon 9 will give the National Reconnaissance Office a busy end to the year. The NROL-108 launch is currently slated for 18 November, using a flight-proven booster flying from Cape Canaveral.

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