Minotaur 1 Mission Preview:
The ORS-1 satellite is the first fully operational spacecraft to be launched as part of the Operationally Responsive Space programme, which has so far seen a series of technology demonstration satellites placed into orbit to test systems for future missions.
Goodrich Corporation is the primary contractor for the ORS-1 mission, and also produced the sensors that will fly aboard it. The satellite is based on the ORS/JWS bus, which was built by Alliant Techsystems. It is the same bus that was used for the earlier TacSat-3 mission. The satellite’s primary instrument is the Senior Year Electro-optical Reconnaissance System 2, or SYERS-2, the same imagery payload carried by the Lockheed U-2 aircraft.
The Tactical Satellite, or TacSat programme, is the primary technology demonstration programme for ORS. To date, two spacecraft have been launched, with a third cancelled and a fourth expected to fly later this year. The programme was originally expected to begin with the TacSat-1 spacecraft, a converted OrbComm satellite which was to have demonstrated the provision of infrared and optical images directly to troops on the battlefield.
The spacecraft was intended to be launched from Vandenberg AFB on the maiden flight of the Falcon 1 rocket in 2005 however the launch was delayed to avoid overflying Space Launch Complex 4E whilst it was occupied by the last Titan IV rocket.
The launch of FalconSat-2 in early 2006 instead became the Falcon 1’s maiden flight, and following its failure, and the failure of a demonstration launch the next year, TacSat-1 was declared obsolete and its launch cancelled. Despite reports that it was to have been refurbished and launched in 2009 as TacSat-1A, it never flew.
TacSat-2 was the first TacSat to fly. It was launched by a Minotaur I from the Mid-Atlantic Regional Spaceport (MARS) in December 2006. Eleven imagery and technology demonstration payloads were carried aboard the satellite, with the primary instrument being the Earth Surface Imager, or ESI.
The mission was officially considered a success, however a reported dispute between the US Navy and National Reconnaissance Office allegedly prevented some of the sensors from being tested for several months, and it remains unclear if they were ever activated. The satellite ceased operations in January 2008, and decayed from orbit on 5 February 2011.
TacSat-3 was launched in May 2009, also on a Minotaur I from MARS. The first spacecraft to be operated under the Operationally Responsive Space Office, it carries a hyperspectral imaging (HSI) payload; the Advanced Responsive Tactically Effective Military Imaging Spectrometer or Artemis.
Following the completion of the experimental phase of its mission, TacSat-3 was brought into service with US Space Command, reportedly as it was able to detect underground tunnels and roadside bombs. TacSat-4, which is currently scheduled to launch on a Minotaur IV in October, will be used for communications experiments.
The United Kingdom has also developed operationally responsive satellites, with the TopSat spacecraft having been launched in October 2005, a year before TacSat-2. TopSat was also used for tests conducted by the United States as part of the TacSat programme, into the distribution of imagery to troops via the internet, and within 90 minutes of the images being produced. The United States military named the satellite TacSat-0 whilst it was being used for these tests.
In addition to the TacSat series, the Operationally Responsive Space office was also to have operated the Trailblazer satellite, which was lost in a launch failure in August 2008.
The primary payload for the third Falcon 1 launch, which was originally to have carried TacSat-1, Trailblazer was selected for launch in May 2008, at the time less than a month before the scheduled launch date, as part of the Jumpstart programme. During launch, residual thrust in the first stage engine led to recontact between the first and second stages, and the rocket subsequently failed to achieve orbit.
ORS-1 was launched by Orbital Sciences Corporation (OSC), using a Minotaur I rocket, which was making its tenth flight. The Minotaur I, which first flew in January 2000, is a four stage solid-fuelled expendable launch system derived from the LGM-30F Minuteman II missile, which was developed in the 1960s and retired from operational service in December 1991.
The Minuteman II was a three stage rocket, consisting of an M-55E1 first stage, an SR-19 second stage, and an M-57A1 third stage. It first flew in September 1964, and made 181 flights concluding with a final operational test in November 1987. All but four of its test launches were successful. In total 668 rockets were built; 48 prototypes and pre-production missiles, before a production run of 620 missiles.
The Minotaur I uses the first two stages of the Minuteman, however it has an Orion-50XL as its third stage, in place of the M-57A1. In addition, an Orion-38 motor is used as a fourth stage, and a Hydrazine Auxiliary Propulsion System (HAPS) can be added as a fifth stage if required, however to date this has never been used on a Minotaur launch.
The payload is encapsulated within a payload fairing, with two sizes available depending on the size of the spacecraft. For this launch the larger fairing, which has a diameter of 1.55 metres will be used. The standard fairing has a diameter of 1.27 metres, and was last used for the launch of USA-225, or NROL-66, in February.
In addition to Minuteman II rockets have also been converted into Multi-Service Launch System (MSLS) and Minotaur II suborbital launch systems. Unlike the Minotaur I, both of these configurations use all three stages of the Minuteman II. MSLS made eight flights between 1996 and 2001, and since 2000 the Minotaur II has made six flights. A further two flights have been made using the Minotaur II+ configuration, which features an SR-73 third stage instead of the M-57A1.
The Minotaur IV is the only of these three to have flown so far, having made three launches to date; all last year. It is an orbital launch system designed to orbit heavier payloads than the Minotaur I is capable of. The Minotaur III is designed for suborbital flights, and the Minotaur V will be able to place payloads into higher orbits than the Minotaur IV; its first flight will be the launch of NASA’s LADEE spacecraft bound for the Moon.
The launch lasted less than twelve minutes from liftoff to spacecraft separation. The flight began at T-0, with the ignition of the first stage to begin the vehicle’s ascent. Two seconds after launch the rocket began its roll and pitch manoeuvres to attain the correct attitude for its climb. Thirty eight seconds into flight the rocket passed through the area of maximum dynamic pressure, or max-Q.
The first stage was expected to burn for around 61.3 seconds, after which it was jettisoned, and the second stage ignited. The interstage between the first and second stages separated from the second stage seventeen seconds after ignition.
The second stage burned for 72 seconds, completing its burn and separating 133 seconds after liftoff. Two seconds after the second stage separates, the third stage ignited for a 73 second burn. About ten seconds after third stage ignition, the payload fairing was successfully jettisoned, exposing the ORS-1 satellite to space for the first time.
Flight controllers will have been watching fairing separation closely since the Minotaur and Taurus rockets have similar fairing separation mechanisms, and this was the first launch OSC have made since a Taurus-XL failed to place the Glory satellite into orbit in early March. It was the second consecutive Taurus launch on which the payload fairing failed to separate, resulting in the rocket being too heavy to reach orbit.
Once the third stage completed its burn, the rocket coasted for 303 seconds, after which the third stage was jettisoned. Then, eleven seconds later, the fourth stage ignited to begin the final powered phase of the mission. This burn lasted 66 seconds, leaving the stage and its payload in an approximately circular orbit at an altitude of 400 kilometres, inclined at 40 degrees to the equator.
Two minutes after fourth stage burnout; eleven minutes and forty eight seconds after lifting off, the spacecraft separated from the fourth stage to begin its mission.
Launch Pad 0B (LP-0B) at the Mid-Atlantic Regional Spaceport was the point of departure for the ORS-1 mission. Pad 0B was built in the mid-1990s as part of NASA’s Wallops Flight Facility, with construction being completed in 1998. Following completion, several modifications have been made to the complex, including the addition of a mobile service tower in 2004.
ORS-1 was the fifth launch from Pad 0B, and the fourth Minotaur to fly from the complex. The first launch from the pad, that of TacSat-2, occurred on 16 December 2006; the day after the eighth anniversary of the end of construction work on the pad. Four months later on 24 April 2007, another Minotaur launched from the facility carrying the NFIRE satellite.
The next launch from the complex was the ALV X-1 mission in August 2008, on the only flight of the experimental ATK Launch Vehicle. The rocket went off course, and was destroyed by range safety twenty seconds into its flight. The most recent launch from LP-0B was of TacSat-3 in May 2009.
The Mid-Atlantic Regional Spaceport is a commercial spaceport operated by the Virginia Commercial Space Flight Authority in conjunction with NASA. It consists of two launch pads; Pad 0B, and Pad 0A. Pad 0A was originally built for Conestoga rockets, however the Conestoga programme was abandoned after the rocket failed on its maiden flight and as a result only one launch was made from LP-0A.
The pad remained dormant until September 2008, when it was demolished to make way for a new launch pad for the Taurus II rocket. The Taurus II is currently expected to make its maiden flight from LA-0A at MARS in October this year.
This was the second launch of a Minotaur rocket this year, following the successful deployment of the USA-225 satellite in February by another Minotaur I. The next Minotaur launches are expected to occur in October, with two Minotaur IVs scheduled to fly that month. One will carry the TacSat-4 spacecraft into an elliptical orbit, whilst the other will carry the HTV-2b hypersonic technology experiment on a suborbital trajectory.
In the same month Orbital Sciences Corporation is also planning to conduct the maiden flight of the Taurus II; a demonstration flight which is not expected to carry a payload.