Pegasus
Pegasus XL attached to mothership Stargazer
Has useLaunch vehicle
ManufacturerNorthrop Grumman
Country of originUnited States
Cost per launchUS$40 million [1]
Size
Height16.9 m (55 ft) (Pegasus)
17.6 m (58 ft) (Pegasus XL)
Diameter1.27 m (4 ft 2 in)
Mass18,500 kg (40,800 lb) (Pegasus)
23,130 kg (50,990 lb) (Pegasus XL)
Stages3
Capacity
Payload to Low Earth orbit
Mass443 kg (977 lb)
Associated rockets
FamilyAir launch to orbit
Derivative workMinotaur-C
ComparableElectron, Vector-H, Falcon 1, Pegasus
Launch history
StatusActive
Launch sitesAir launch to orbit
Total launches45
Success(es)40
Failure(s)3
Partial failure(s)2
First flight5 April 1990
(Pegsat / NavySat)
Last flight13 June 2021
(TacRL-2 / Odyssey)

Pegasus is an air-launched launch vehicle developed by Orbital Sciences Corporation (OSC) and now built and launched by Northrop Grumman. Capable of carrying small payloads of up to 443 kg (977 lb) into low Earth orbit, Pegasus first flew in 1990 and remains active as of 2021. The vehicle consists of three solid propellant stages and an optional monopropellant fourth stage. Pegasus is released from its carrier aircraft at approximately 12,000 m (39,000 ft), and its first stage has a wing and a tail to provide lift and attitude control while in the atmosphere. Notably, the first stage does not have a thrust vector control (TVC) system.[1]

History

Pegasus was designed by a team led by Antonio Elias.[2] The Pegasus's three Orion solid motors were developed by Hercules Aerospace (later Alliant Techsystems) specifically for the Pegasus launcher but using advanced carbon fiber, propellant formulation and case insulation technologies originally developed for the terminated USAF Small ICBM program. The wing and fins' structures were designed by Burt Rutan and his company, Scaled Composites, which manufactured them for Orbital.

Started in the spring of 1987,[3] the development project was funded by Orbital Sciences Corporation and Hercules Aerospace, and did not receive any government funding. Government funding was received to support operational testing.[4] NASA did provide the use of the B-52 carrier aircraft on a cost-reimbursable basis during the development (captive carry tests) and the first few flights. Two Orbital internal projects, the Orbcomm communications constellation and the OrbView observation satellites, served as anchor customers to help justify the private funding.[5]


There were no Pegasus test launches prior to the first operational launch on 5 April 1990 with NASA test pilot and former astronaut Gordon Fullerton in command of the carrier aircraft. Initially, a NASA-owned B-52 Stratofortress NB-008 served as the carrier aircraft. By 1994, Orbital had transitioned to their "Stargazer" L-1011, a converted airliner which was formerly owned by Air Canada. The name "Stargazer" is an homage to the television series Star Trek: The Next Generation: the character Jean-Luc Picard was captain of a ship named Stargazer prior to the events of the series, and his first officer William Riker once served aboard a ship named Pegasus.[6]

During its 45-launch history, the Pegasus program had three mission failures (STEP-1, STEP-2 and HETI/SAC-B), and two partial failures, (USAF Microsat and STEP-2) followed by 30 consecutive successful flights for a total program success rate of 89 percent.[7] The first partial failure on 17 July 1991 caused the seven USAF microsatellites to be delivered to a lower than planned orbit, significantly reducing the mission lifetime. The last mission failure on 4 November 1996 resulted in the loss of gamma-burst identifying satellite HETE (High Energy Transient Explorer) in 1996.[8]

Preparations for launch of Pegasus XL carrying the NASA Interstellar Boundary Explorer (IBEX) spacecraft.
Preparations for launch of Pegasus XL carrying the NASA Interstellar Boundary Explorer (IBEX) spacecraft.
The Pegasus XL with fairing removed exposing payload bay and the IBEX satellite.
The Pegasus XL with fairing removed exposing payload bay and the IBEX satellite.

The Pegasus XL, introduced in 1994[citation needed] has lengthened stages to increase payload performance. In the Pegasus XL, the first and second stages are lengthened into the Orion 50SXL and Orion 50XL, respectively. Higher stages are unchanged; flight operations are similar. The wing is strengthened slightly to handle the higher weight. The standard Pegasus has been discontinued; the Pegasus XL is still active as of 2019. Pegasus has flown 44 missions in both configurations, launching 91 satellites as of October 12, 2019.[9][10]

Dual payloads can be launched, with a canister that encloses the lower spacecraft and mounts the upper spacecraft. The upper spacecraft deploys, the canister opens, then the lower spacecraft separates from the third-stage adapter. Since the fairing is unchanged for cost and aerodynamic reasons, each of the two payloads must be relatively compact. Other multiple-satellite launches involve "self-stacking" configurations, such as the ORBCOMM spacecraft.

For their work in developing the rocket, the Pegasus team led by Antonio Elias was awarded the 1991 National Medal of Technology by U.S. President George H. W. Bush.

The initial launch price offered was US$6 million, without options or a HAPS (Hydrazine Auxiliary Propulsion System) maneuvering stage. With the enlargement to Pegasus XL and the associated improvements to the vehicle, baseline prices increased. In addition, customers usually purchase additional services, such as extra testing, design and analysis, and launch-site support.[11]

As of 2015, the most recent Pegasus XL to be purchased — a planned June 2017 launch of NASA's Ionospheric Connection Explorer (ICON) mission — had a total cost of US$56.3 million, which NASA notes includes "firm-fixed launch service costs, spacecraft processing, payload integration, tracking, data and telemetry and other launch support requirements".[11] A series of technical problems delayed this launch, which finally took place on 11 October 2019.

In July 2019, it was announced that Northrop Grumman had lost the launch contract of the Imaging X-ray Polarimetry Explorer (IXPE) satellite to SpaceX. IXPE had been planned to be launched by a Pegasus XL rocket, and had been designed so as to fit within the Pegasus XL rocket constraints. With the IXPE launch removed from the Pegasus XL rocket, there are currently (as of 12 October 2019, after the launch of ICON) no space launch missions announced for the Pegasus XL rocket. The future (under construction as of 2019) NASA Explorer program mission Polarimeter to Unify the Corona and Heliosphere (PUNCH) was planned to be launched by Pegasus XL; but then NASA decided to merge the launches of PUNCH and another Explorer mission, Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) (also under construction as of 2019). These two space missions, consisting of 6 satellites in total, are to be launched by one launch vehicle. It is expected that a larger launcher will be chosen for this dual mission launch.[12]

Northrop has two Pegasus XL's remaining in its inventory. It is looking for customers for those rockets. Northrop does not plan on retiring the Pegasus XL rocket as of October 2019.[13]

Launch profile

Orbital's Lockheed  L-1011 Stargazer launches Pegasus carrying the three Space Technology 5 satellites, 2006
Orbital's Lockheed L-1011 Stargazer launches Pegasus carrying the three Space Technology 5 satellites, 2006
Pegasus engine fires following release from its host, a Boeing B-52 Stratofortress, 1991
Pegasus engine fires following release from its host, a Boeing B-52 Stratofortress, 1991

In a Pegasus launch, the carrier aircraft takes off from a runway with support and checkout facilities. Such locations have included Kennedy Space Center / Cape Canaveral Air Force Station, Florida; Vandenberg Air Force Base and Dryden Flight Research Center, California; Wallops Flight Facility, Virginia; Kwajalein Range in the Pacific Ocean, and the Canary Islands in the Atlantic Ocean. Orbital offers launches from Alcantara, Brazil, but no known customers have performed any.

Upon reaching a predetermined staging time, location, and velocity the aircraft releases the Pegasus. After five seconds of free-fall, the first stage ignites and the vehicle pitches up. The 45-degree delta wing (of carbon composite construction and double-wedge airfoil) aids pitch-up and provides some lift. The tail fins provide steering for first-stage flight, as the Orion 50S motor does not have a thrust-vectoring nozzle.

Approximately 1 minute and 17 seconds later, the Orion 50S motor burns out. The vehicle is at over 200,000 feet (61 km) in altitude and hypersonic speed. The first stage falls away, taking the wing and tail surfaces, and the second stage ignites. The Orion 50 burns for approximately 1 minute and 18 seconds. Attitude control is by thrust vectoring the Orion 50 motor around two axes, pitch and yaw; roll control is provided by nitrogen thrusters on the third stage.[citation needed]

Midway through second-stage flight, the launcher has reached a near-vacuum altitude. The fairing splits and falls away, uncovering the payload and third stage. Upon burnout of the second-stage motor, the stack coasts until reaching a suitable point in its trajectory, depending on mission. Then the Orion 50 is discarded, and the third stage's Orion 38 motor ignites. It too has a thrust-vectoring nozzle, assisted by the nitrogen thrusters for roll. After approximately 64 seconds, the third stage burns out.[citation needed]

A fourth stage is sometimes added for a higher altitude, finer altitude accuracy, or more complex maneuvers. The HAPS (Hydrazine Auxiliary Propulsion System) is powered by three restartable, monopropellant hydrazine thrusters. As with dual launches, the HAPS cuts into the fixed volume available for payload. In at least one instance, the spacecraft was built around the HAPS.

Guidance is via a 32-bit computer and an IMU. A GPS receiver gives additional information. Due to the air launch and wing lift, the first-stage flight algorithm is custom-designed. The second- and third-stage trajectories are ballistic, and their guidance is derived from a Space Shuttle algorithm.[citation needed]

Carrier aircraft

Main article: Stargazer (aircraft)

The carrier aircraft (initially a NASA B-52, now an L-1011 owned by Orbital) serves as a booster to increase payloads at reduced cost. 12,000 m (39,000 ft) is only about 4% of a low Earth orbital altitude, and the subsonic aircraft reaches only about 3% of orbital velocity, yet by delivering the launch vehicle to this speed and altitude, the reusable aircraft replaces a costly first-stage booster.

In October 2016, Orbital ATK announced a partnership with Stratolaunch Systems to launch Pegasus-XL rockets from the giant Scaled Composites Stratolaunch, which could launch up to three Pegasus-XL rockets on a single flight.[14]

Related projects

Pegasus XL at the Steven F. Udvar-Hazy Center
Pegasus XL at the Steven F. Udvar-Hazy Center

Pegasus components have also been the basis of other Orbital Sciences Corporation launchers.[15] The ground-launched Taurus rocket places the Pegasus stages and a larger fairing atop a Castor 120 first stage, derived from the first stage of the MX Peacekeeper missile. Initial launches used refurbished MX first stages.

The Minotaur I, also ground-launched, is a combination of stages from Taurus launchers and Minuteman missiles, hence the name. The first two stages are from a Minuteman II; the upper stages are Orion 50XL and 38. Due to the use of surplus military rocket motors, it is only used for U.S. Government and government-sponsored payloads.[why?]

A third vehicle is dubbed Minotaur IV despite containing no Minuteman stages. It consists of a refurbished MX with an Orion 38 added as a fourth stage.

The NASA X-43A hypersonic test vehicles were boosted by Pegasus first stages. The upper stages were replaced by exposed models of a scramjet-powered vehicle. The Orion stages boosted the X-43 to its ignition speed and altitude, and were discarded. After firing the scramjet and gathering flight data, the test vehicles also fell into the Pacific.

The most numerous derivative of Pegasus is the booster for the Ground-based Midcourse Defense (GBMD) interceptor, basically a vertical (silo) launched Pegasus minus wing and fins, and with the first stage modified by addition of a Thrust Vector Control (TVC) system.

Launch statistics

Rocket configurations[edit]

1
2
3
4
5
6
  •   Standard
  •   XL
  •   Hybrid

Launch sites[edit]

1
2
3
4
5
6
1990
1995
2000
2005
2010
2015
2020
  •   Edwards AFB
  •   Kennedy Space Center
  •   Cape Canaveral
  •   Vandenberg
  •   Base Aerea de Gando
  •   Wallops Flight Facility
  •   Kwajalein Atoll

Launch outcomes[edit]

1
2
3
4
5
6
1990
1995
2000
2005
2010
2015
2020
  •   Failure
  •   Partial failure
  •   Success
  •   Planned

Carrier airplane[edit]

1
2
3
4
5
6
1990
1995
2000
2005
2010
2015
2020
  •   B-52
  •   L-1011

Launch history

Pegasus has flown 45 missions between 1990 and 2021.[9]

Flight No. Date / time (UTC) Rocket,
Configuration
Launch site Payload Payload mass Target Orbit [16] Actual Orbit [16] Customer Launch
outcome
1 5 April 1990
19:10:17
Standard (B-52) Edwards AFB Pegsat, NavySat 320.0 x 360.0 km @ 94.00° i 273.0 x 370.0 km @ 94.15° i Success
2 17 July 1991
17:33:53
Standard w/ HAPS (B-52) Edwards AFB Microsats (7 satellites) 389.0 x 389.0 km @ 82.00° i 192.4 x 245.5 km @ 82.04° i Partial failure
Orbit too low, spacecraft reentered after 6 months instead of planned 3-years lifetime.
3 9 February 1993
14:30:34
Standard (B-52) Kennedy Space Center SCD-1 405.0 x 405.0 km @ 25.00° i 393.0 x 427.0 km @ 24.97° i Success
4 25 April 1993
13:56:00
Standard (B-52) Edwards AFB ALEXIS – Array of Low Energy X-ray Imaging Sensors 400.0 x 400.0 km @ 70.00° i 404.0 x 450.5 km @ 69.92° i Success
5 19 May 1994
17:03
Standard w/ HAPS (B-52) Edwards AFB STEP-2 (Space Test Experiments Platform/Mission 2/SIDEX) 450.0 x 450.0 km @ 82.00° i 325.0 x 443.0 km @ 81.95° i Partial failure
Orbit slightly low
6 27 June 1994
21:15
XL (L-1011) Vandenberg AFB STEP-1 (Space Test Experiments Platform/Mission 1) - - Failure
Loss of vehicle control 35 seconds into flight, flight terminated.
7 3 August 1994
14:38
Standard (B-52) Edwards AFB APEX 195.0 x >1000 km @ 70.02° i 195.5 x 1372.0 km @ 69.97° i Success
8 3 April 1995
13:48
Hybrid (L-1011)[a] Vandenberg AFB Orbcomm (2 satellites), OrbView 1 398.0 x 404.0 km @ 70.00° i 395.0 x 411.0 km @ 70.03° i Success
9 22 June 1995
19:58
XL (L-1011) Vandenberg AFB STEP-3 (Space Test Experiments Platform/Mission 3) - - Failure
Destroyed during second-stage flight
10 9 March 1996
01:33
XL (L-1011) Vandenberg AFB REX II 450.0 x 443.0 km @ 90.00° i 450.9 x 434.3 km @ 89.96° i Success
11 17 May 1996
02:44
Hybrid (L-1011) Vandenberg AFB MSTI-3 298.0 x 394.0 km @ 97.13° i 293.0 x 363.0 km @ 97.09° i Success
12 2 July 1996
07:48
XL (L-1011) Vandenberg AFB TOMS-EP 340.0 x 955.0 km @ 97.40° i 341.2 x 942.9 km @ 97.37° i Success
13 21 August 1996
09:47:26
XL (L-1011) Vandenberg AFB FAST (Fast Auroral Snapshot Explorer) 350.0 x 4200.0 km @ 83.00° i 350.4 x 4169.6 km @ 82.98° i Success
14 4 November 1996
17:08:56
XL (L-1011) Wallops Flight Facility HETE, SAC-B 510.0 x 550.0 km @ 38.00° i 488.1 x 555.4 km @ 37.98° i Failure
Satellites not ejected from third stage
15 21 April 1997
11:59:06
XL (L-1011) Gando Air Base, Gran Canaria, Spain Minisat 01, Celestis space burial 587.0 x 587.0 km @ 151.01° i 562.6 x 581.7 km @ 150.97° i Success
16 August 1, 1997
20:20:00
XL (L-1011) Vandenberg AFB OrbView-2 310.0 x 400.0 km @ 98.21° i 300.0 x 302.0 km @ 98.28° i Success
On the line with partial success
17 August 29, 1997
15:02:00
XL (L-1011) Vandenberg AFB FORTE 800.0 x 800.0 km @ 70.00° i 799.9 x 833.4 km @ 69.97° i Success
18 October 22, 1997
13:13:00
XL (L-1011) Wallops Flight Facility STEP-4 (Space Test Experiments Platform/Mission 4) 430.0 x 510.0 km @ 45.00° i 430.0 x 511.0 km @ 44.98° i Success
19 December 23, 1997
19:11:00
XL w/ HAPS (L-1011) Wallops Flight Facility Orbcomm (8 satellites) 825.0 x 825.0 km @ 45.00° i 822.0 x 824.0 km @ 45.02° i Success
20 February 26, 1998
07:07:00
XL (L-1011) Vandenberg AFB SNOE, BATSAT 580.0 x 580.0 km @ 97.75° i 582.0 x 542.0 km @ 97.76° i Success
21 April 2, 1998
02:42:00
XL (L-1011) Vandenberg AFB TRACE 600.0 x 650.0 km @ 97.88° i 599.9 x 649.2 km @ 97.81° i Success
22 August 2, 1998
16:24:00
XL w/ HAPS (L-1011) Wallops Flight Facility Orbcomm (8 satellites) 818.5 x 818.5 km @ 45.02° i 819.5 x 826.0 km @ 45.01° i Success
23 September 23, 1998
05:06:00
XL w/ HAPS (L-1011) Wallops Flight Facility Orbcomm (8 satellites) 818.5 x 818.5 km @ 45.02° i 811.0 x 826.0 km @ 45.02° i Success
24 October 22, 1998
00:02:00
Hybrid (L-1011) Cape Canaveral SCD-2 750.0 x 750.0 km @ 25.00° i 750.4 x 767.0 km @ 24.91° i Success
25 December 6, 1998
00:57:00
XL (L-1011) Vandenberg AFB SWAS 635.0 x 700.0 km @ 70.00 ° i 637.7 x 663.4 km @ 69.91° i Success
26 March 5, 1999
02:56:00
XL (L-1011) Vandenberg AFB WIRE – Wide Field Infrared Explorer 540.0 x 540.0 km @ 97.56° i 539.0 x 598.0 km @ 97.53° i Success
27 May 18, 1999
05:09:00
XL w/ HAPS (L-1011) Vandenberg AFB Terriers, MUBLCOM 550.0 x 550.0 km @ 97.75° i,


775.0 x 775.0 km @ 97.75° i

551.0 x 557.0 km @ 97.72° i,


774.0 x 788.0 km @ 97.72° i

Success
28 December 4, 1999
18:53:00
XL w/ HAPS (L-1011) Wallops Flight Facility Orbcomm (7 satellites) 825.0 x 825.0 km @ 45.02° i 826.5 x 829.0 km @ 45.02° i Success
29 June 7, 2000
13:19:00
XL (L-1011) Vandenberg AFB TSX-5 (Tri-Service-Experiments mission 5) 405.0 x 1.750.0 km @ 69.00° i 409.9 x 1,711.7 km @ 68.95° i Success
30 October 9, 2000
05:38:00
Hybrid (L-1011) Kwajalein Atoll HETE 2 600.0 x 650.0 km @ 2.00° i 591.9 x 651.9 km @ 1.95° i Success
31 February 5, 2002
20:58:00
XL (L-1011) Cape Canaveral RHESSI 600.0 x 600.0 km @ 38.00° i 586.4 x 602.0 km @ 38.02° i Success
32 January 25, 2003
20:13:00
XL (L-1011) Cape Canaveral SORCE 645.0 x 645.0 km @ 40.00° i 622.3 x 647.3 km @ 39.999° i Success
33 April 28, 2003
12:00:00
XL (L-1011) Cape Canaveral GALEX – Galaxy Evolution Explorer 690.0 x 690.0 km @ 29.00° i 689.8 x 711.3 km @ 28.99° i Success
34 June 26, 2003
18:55:00
XL (L-1011) Vandenberg AFB OrbView-3 369.0 x 470.0 km @ 97.29° i 367.1 x 440.5 km @ 97.27° i Success
35 August 13, 2003
02:09:00
XL (L-1011) Vandenberg AFB SCISAT-1 650.0 x 650.0 km @ 73.92° i 647.9 x 659.7 km @ 73.95° i Success
36 April 15, 2005
17:27:00
XL w/ HAPS (L-1011) Vandenberg AFB DART 538.7 x 566.7 km @ 97.73° i 541.2 x 548.8 km @ 97.73° i Success
37 March 22, 2006
14:03:00
XL (L-1011) Vandenberg AFB ST-5 – Space Technology 5 (3 satellites) 300.0 x 4500.0 km @ 105.6° i 301.1 x 4571.0 km @ 105.62° i Success
38 April 25, 2007
20:26:00
XL (L-1011) Vandenberg AFB AIM – Aeronomy of Ice in the Mesosphere 197 kg (434 lb)[18] 600.0 x600.0 km @ 97.77° i 601.3 x 596.2 km @ 97.79° i NASA[18] Success
39 April 16, 2008
17:01:00
XL (L-1011) Kwajalein Atoll C/NOFS 384 kg (847 lb)[19] 400.0 x 850.0 km @ 13.0° i 401.0 x 868.0 km @ 12.99° i STP / AFRL / DMSG[19] Success
40 October 19, 2008
17:47:23
XL (L-1011) Kwajalein Atoll IBEX – Interstellar Boundary Explorer 107 kg (236 lb)[20] 207.0 x 412.0 km @11.0° i 206.4 x 445.0 km @ 10.99° i NASA Success
41 June 13, 2012
16:00:00
XL (L-1011) Kwajalein Atoll NuSTAR – Nuclear Spectroscopic Telescope Array 350 kg (770 lb)[21] ≥530.0 x ≤660.0 km @ 5.0 – 7.0° i 621.2 x 638.5 km @ 6.024° i NASA / JPL Success [22]
42 June 28, 2013
02:27:46 [23]
XL (L-1011) Vandenberg AFB IRIS – Interface Region Imaging Spectrograph SMEX 183 kg (403 lb)[24] ≥620.0 x ≤670.0 km @97.89° i 622.9 x 669.3 km @ 97.894° i NASA Success [24]
43 December 15, 2016
13:37:00
XL (L-1011) Cape Canaveral Cyclone Global Navigation Satellite System (CYGNSS)[25] 345.6 kg (762 lb)[26] 510.0 x 6888.0 km @ 35° i 511.5 x 6908.1 km @ 34.97° i NASA Success[27]
44 11 October 2019
01:59:05
XL (L-1011) Cape Canaveral Ionospheric Connection Explorer (ICON) 281 kg (619 lb) [28][29] LEO, 590 x 607 km[29] 608.4 x 571.6 @ 26.98° i UC Berkeley SSL / NASA Success [30]
45 13 June 2021
08:11 [31][32]
XL (L-1011) Vandenberg Space Force Base TacRL-2 (Odyssey) 325 kg (717 lb) LEO
-
U.S. Space Force Success
  1. ^ The "Hybrid" Pegasus, sometimes called Pegasus H, is a Standard Pegasus that has been modified with canted fins similar to those on the Pegasus XL in order to be launched by the Stargazer carrier aircraft [17]

Planned launches

Date / time (UTC) Rocket,
Configuration
Launch site Payload Orbit Customer

Launch failures

Partial successes

See also

References

  1. ^ a b c "Pegasus User's Guide" (PDF). Orbital-ATK. October 2015. Archived from the original (PDF) on 13 January 2016.
  2. ^ Brown, Stuart (May 1989), "Winging it Into Space", The Popular Science Monthly, Popular Science: 128, ISSN 0161-7370, retrieved 27 June 2013
  3. ^ Thompson, David (2007), An Adventure Begins - Orbital's First 25 Years, Orbital Sciences Corporation
  4. ^ Mosier, Marty; Harris, Gary; Richards, Bob; Rovner, Dan; Carroll, Brent (1990). "Pegasus First Mission Flight results". Proceedings of the 4th AIAA/USU Conference on Small Satellites. 1. Bibcode:1990aiaa....1.....M.
  5. ^ Rebecca Hackler (3 June 2013). "NASA Johnson Space Center Oral History Project Commercial Crew & Cargo Program Office Edited Oral History Transcript". NASA. Public Domain This article incorporates text from this source, which is in the public domain.
  6. ^ "startrek.com". startrek.com.
  7. ^ NASA reviews space access after second Pegasus failure
  8. ^ Pegasus clings to its satellite cargo.
  9. ^ a b "Pegasus Mission History" (PDF). Northrop Grumman.
  10. ^ "Pegasus Rocket".
  11. ^ a b "NASA Awards Launch Services Contract for Ionospheric Connection Explorer". NASA. 26 September 2017. Public Domain This article incorporates text from this source, which is in the public domain.
  12. ^ Clark, Stephen (8 July 2019). "SpaceX wins NASA contract to launch X-ray telescope on reused rocket". Spaceflight Now. Retrieved 10 July 2019.
  13. ^ "Rockets purchased by Stratolaunch back under Northrop Grumman control – Spaceflight Now".
  14. ^ Foust, Jeff (6 October 2016). "Stratolaunch to launch Pegasus rockets". SpaceNews. Retrieved 7 June 2018.
  15. ^ Barron Beneski (6 December 2011). "Letter: "Qualified Success" Sells Pegasus Short". SpaceNews.
  16. ^ a b "Pegasus Payload User's Guide" (PDF). Northrop Grumman. September 2020. pp. 111–113.
  17. ^ Graham, William (13 June 2021). "Pegasus XL rocket to carry out Tactically Responsive Launch demo for Space Force". NASASpaceFlight.com.
  18. ^ a b ESA. "AIM (Aeronomy of Ice in the Mesosphere)". Retrieved 31 March 2020.
  19. ^ a b ESA. "C/NOFS (Communication/Navigation Outage Forecast System)". Retrieved 31 March 2020.
  20. ^ "IBEX - eoPortal Directory - Satellite Missions". directory.eoportal.org. Retrieved 31 March 2020.
  21. ^ "Nuclear Spectroscopic Telescope Array, or NuSTAR" (PDF). June 2012. Retrieved 16 June 2012.
  22. ^ "NuSTA" (PDF). December 2010. Archived from the original (PDF) on 17 July 2011.
  23. ^ "NASA's Consolidated Launch Schedule". NASA. 14 May 2013.
  24. ^ a b "IRIS Launch Coverage". NASA. 27 June 2013.
  25. ^ "NASA Awards Launch for Orbital's Pegasus Rocket". Orbital press release. 1 April 2014.
  26. ^ "Pegasus launches CYGNSS constellation following Stargazer release". NASASpaceFlight.com. 15 December 2016. Retrieved 29 March 2020.
  27. ^ Graham, William (15 December 2016). "Pegasus launches CYGNSS constellation following Stargazer release". NASASpaceFlight. Retrieved 16 December 2016.
  28. ^ Clark, Stephen (10 November 2017). "Launch of NASA ionospheric probe delayed to examine rocket issue". Spaceflight Now. Retrieved 29 March 2020.
  29. ^ a b "ICON Fast acts". icon.ssl.berkeley.edu. Retrieved 29 March 2020.
  30. ^ Gebhardt, Chris (11 October 2019). "NASA's ICON mission launches on Northrop Grumman Pegasus XL rocket". NASASpaceFlight.com. Retrieved 11 October 2019.
  31. ^ Erwin, Sandra (10 June 2021). "U.S. Space Force to launch "space domain awareness" satellite on Pegasus rocket". SpaceNews. Retrieved 10 June 2021.
  32. ^ Clark, Stephen (17 March 2021). "Northrop Grumman's Pegasus rocket selected for responsive launch demo". Spaceflight Now. Retrieved 29 April 2021.
  33. ^ International reference guide to space launch systems, Fourth edition, page 290, ISBN 1-56347-591-X