The Delta II rocket has made what could be its final flight Friday, deploying a new weather and environmental research satellite for NASA and the United States National Oceanic and Atmospheric Administration, along with six CubeSats. Liftoff from Space Launch Complex 2W at Vandenberg Air Force Base in California was on schedule at 09:48 UTC (02:48 PDT) Friday morning.
The NPOESS Preparatory Project, or NPP, satellite was originally developed as a pathfinder for the NPOESS programme. Following the cancellation of NPOESS, it will instead be used operationally. It was constructed by Ball Aerospace, and is based around the BCP-2000 satellite bus. NPP is a 1,976-kilogram satellite, with a planned mission duration of five years; however the spacecraft has a design life of seven years, and could remain operational for longer.
NPOESS was intended to combine the roles currently performed by the military Defense Meteorological Support Program (DMSP), mad the civilian Earth Observing System (EOS) and Polar Orbiting Environmental Satellites (POES), and which are used for military and civilian weather observation respectively. The programme was abandoned last year as it was over budget and behind schedule.
Instead, DMSP will be replaced by the Defense Weather Satellite System (DWSS), which is expected to enter service at the end of the decade, whilst the Joint Polar Satellite System (JPSS) will replace POES. NPP is intended to bridge the gap between EOS and JPSS, and will also serve as the first JPSS satellite to be launched. A second satellite, JPSS-1, scheduled for launch in 2014. JPSS-1 will be based on the NPP spacecraft.
Five instruments aboard NPP will be used to return data about Earth’s environment and atmosphere. The Visible Infrared Imaging Radiometer Suite, VIIRS, will be used to produce visible-light and infrared imagery of the Earth’s surface, at 22 different wavelengths. The images will be used to monitor a wide range of phenomena on the Earth’s surface.
The second instrument, Clouds and the Earth’s Radiant Energy System (CERES), is identical to four existing instruments currently in orbit; two aboard Terra and two aboard Aqua. It will be used to study the Earth’s radiation budget; monitoring the amount of energy emitted and reflected by the planet.
The Cross-track Infrared Microwave Sounding Suite, CrIMSS, is comprised of two instruments; the Cross-track Infrared Sounder (CrIS) and the Advanced Technology Microwave Sounder (ATMS). CrIMSS will be used to profile the temperature and humidity of the atmosphere.
CrIS will operate at infrared wavelengths, whilst ATMS will operate at much shorter, microwave, wavelengths. The data returned by the two instruments will be used to help meteorologists better understand individual storms, and to provide data for weather forecasts.
The Ozone Mapping and Profiler Suite, or OPMS, is the final instrument aboard NPP. It will be used to measure ozone levels and distribution in the troposphere, and in the upper atmosphere. That data it is expected to return will allow scientists to study the ozone distribution at a higher resolution than previous instruments. Data will also be used to forecast the ultraviolet exposure of humans in particular areas, and to monitor air quality.
ELaNa III, which will be launched along with NPP, is part of NASA’s Educational Launch of Nanosatellites, or ELaNa, programme. ElaNa is intended to provide US educational institutions with the opportunity to develop and operate spacecraft. It consists of six CubeSats, which will conduct a variety of missions.
The CubeSats, loaded into three CalPoly PPODs attached to the second stage of the Delta II, will separate from the carrier rocket during a coast phase between the second stage’s two propellant depletion burns following the separation of NPP. This is the first time a Delta II has deployed CubeSats, despite the fact that the PPOD deployment mechanism was originally designed for use on the Delta II’s second stage.
E1P-U2, or Explorer-1 [PRIME] Unit 2, was originally built as a flight spare for the Explorer-1 [PRIME] (E1P) satellite, which was lost in the failure of a Taurus-XL rocket earlier this year. E1P was itself a replacement for MEROPE, which was lost in a Dnepr launch failure in 2006. The objective of the spacecraft’s mission is to refly the radiation experiment carried by America’s first satellite, Explorer 1, using modern technology.
The original experiment led to the discovery of the Van Allen belts, and E1P was intended to be launched in 2008 to mark the fiftieth anniversary of the discovery. Funded by the Montana Space Grant Consortium, the spacecraft will be operated by the University of Montana. It is a single-unit CubeSat which will be deployed from PPOD-1, and is expected to operate for four months.
Auburn University’s AubieSat-1 is also flying in PPOD-1. Like E1P-U2, it is a single-unit CubeSat. The Alabama Space Grant Consortium has provided funding for the mission, which will study the use of two different types of film to protect the spacecraft’s solar cells.
It will also investigate the propagation of radio waves within the Earth’s ionosphere.
The final spacecraft in PPOD-1, M-Cubed, will be operated by the University of Michigan. It carries an earth imagery payload, consisting of a 2 megapixel camera with a fifty degree field-of-view and a 2.8 millimetre focal length. A secondary payload, the CubeSat On-Board Processing Validation Experiment, was developed by NASA’s Jet Propulsion Laboratory, and will process the images produced by the satellite’s camera.
The University of Michigan will also operate the Radio Auroral Explorer 2 (RAX-2) satellite; a three-unit CubeSat which fully occupies PPod-3.
It will study the effects of the Earth’s magnetic field on the spacecraft’s orbit by using high-resolution narrow beam radar to study small changes in the spacecraft’s altitude, in order to map the relationship between such changes and the magnetic field lines.
PPOD-2 contains the Dynamic Ionosphere CubeSat Experiment, or DICE, which will use two satellites to observe periodic storms in the ionosphere occurring primarily over the United States. Such storms can disrupt radio signals travelling through the ionosphere, disrupting satellite communication and navigation services. The satellites are both 1.5 unit CubeSats, measuring 15x10x10 centimetres. They will be operated by Utah State University.
The next ELaNa mission is scheduled for next July, when three PPODs will be launched aboard an Atlas V 411 rocket along with NROL-36; a classified payload for the US National Reconnaissance Office, which is likely to be a pair of Naval Ocean Surveillance System satellites. Following this, the second and third SpaceX Dragon launches under the CRS programme will carry four and five PPODs respectively.
NPP was launched by a Delta II rocket, flying from Space Launch Complex 2W at the Vandenberg Air Force Base in California. The rocket, Delta 357, was the 151st Delta II to be launched, and flew in the Delta II 7920-10C configuration.
It was the last Delta II currently manifested to launch, however the type has recently been returned to NASA’s Launch Services II (NLS-II) contract, with as many as five launches possible in coming years. It remains unclear as to whether these will actually fly, however, so Delta 357 may well be the last Delta II to fly.
The Delta II is, itself, the last of the Thor-Delta series of rockets, and its first stage is the final incarnation of the Thor rocket, which began life as an intercontinental ballistic missile in the 1950s. The first Thor was launched from Launch Complex 17B at Cape Canaveral on 26 January 1957.
A valve failure led to an immediate loss of thrust, with the rocket falling back onto the launch pad and exploding. The second flight, on 20 April 1957 was not much more successful after the rocket was accidentally destroyed range safety.
The first successful Thor launch came at the fourth attempt, on 20 September 1957. Production began later that year, with the first missiles becoming operational in 1958. Project Emily, begun in 1959, saw sixty Thor missiles transferred to the Royal Air Force, and stationed in the United Kingdom.
RAF crews also conducted launches from Vandenberg Air Force Base, testing the missiles, and providing experience for their operators. The missiles returned to the United States in 1963, marking the end of Thor’s operational life as a ballistic missile.
Several Thor missiles were subsequently deployed as anti-satellite weapons, and some were used for suborbital tests, including the ASSET reentry vehicles, whilst the majority were converted to launch satellites.
Thor was already established as an orbital launch system, having made its first orbital launch attempt in 1958, when a Thor DM-18 Able I failed to place a Pioneer spacecraft into orbit.
The Thor-Agena entered service the next year, and the first successful orbital launch of a Thor occurred on 13 April 1959, when Discoverer 2 was launched by the second Thor DM-18 Agena-A.
The Thor-Ablestar, which entered service in 1960, was the first rocket to incorporate a restartable upper stage. The Ablestar upper stage was an enlarged version of the Able stage, which had been used previously on the Vanguard rocket. The Delta upper stage was also derived from Able.
The first Thor-Delta launch occurred on 13 May 1960, and failed to place the Echo 1 communications satellite into orbit. Another attempt on 12 August the same year successfully lofted a replacement, Echo 1A.
The ninth Delta launch, in April 1962, carried the first satellite to be operated by a country other than the United States or the Soviet Union, the United Kingdom’s Ariel 1. Despite being operated by the United Kingdom, Ariel 1 was constructed in the United States, and later in 1962, a Thor DM-21 Agena-B launched the first satellite to be constructed by a country other than the USA or USSR; Canada’s Alouette 1.
Through the 1960s the Thor-Delta evolved, with its payload capacity being increased by changes to its stages, and the addition of boosters. In 1967 these changes were incorporated back into the Thor-Agena, resulting in the Thorad-Agena, which featured a stretched first stage originally developed for the Delta. Each development of the Delta rocket was designed using a sequential letter of the alphabet, and by the end of 1969, the Delta-N was in service.
The next upgrade, introduced in 1972, brought with it a new designation system. Each variant was identified by a four digit number; the first digit identifying the type of first stage and boosters, the second digit identifying the number of boosters, the third digit identifying the second stage, and the fourth digit identifying the third stage.
In 1975, the N-I made its first flight from the Osaki Launch Complex at the Tanegashima Space Center in Japan. It consisted of a Thor first stage which was built under license, with a Japanese second stage. The N-II, which first flew in 1981, was a fully-license-produced Thor-Delta. The third variant built by Japan, the H-I, consisted like the N-I of a Thor first stage, and a Japanese second stage. It was developed into the all-Japanese H-II, which in turn was developed into to the current H-IIA and H-IIB.
In 1982, the Delta 3920 made its first flight, introducing the Delta-K upper stage, which is still in service on the Delta II. By this stage, however, the Space Shuttle was flying, and the Delta programme was coming to an end, as expendable launch systems were believed to be obsolete.
Following the Challenger accident in 1986, payloads began to transfer back to expendable rockets, with the US Air Force transferring its GPS satellites to Delta. This resulted in the development of the Delta II, which first flew on 14 February 1989.
The initial Delta II launches were of the interim 6000-series configuration, with an Extra-Extended Long Tank Thor first stage powered by a single RS-27 engine, and augmented by nine Castor-4A solid rocket motors. When the 7000 series flew in November 1990, it replaced the RS-27 with an uprated RS-27A engine, and replaced the Castors with GEM-40 motors. Seventeen 6000-series rockets were launched before the type was phased out.
In addition, six 7000H-series rockets, with GEM-46 solids have also been launched, with the “Heavy” making its final flight last month carrying the GRAIL spacecraft bound for the moon.
During its 22 years in service, the Delta II has only experienced two launch failures, and it is statistically the most reliable rocket in service. The first of the two failures occurred in August 1995, when the Koreasat 1 spacecraft was left in a significantly lower orbit than planned after a solid rocket motor failed to separate from the rocket.
Despite the shortfall, Koreasat 1 was eventually able to reach its operational orbit, but not without expending a significant amount of its propellant, thereby shortening its operational life.
In January 1997, Delta 241 lifted off from Cape Canaveral carrying GPS IIR-1, the first in a new series of GPS satellites. Thirteen seconds later it exploded, showering 220 tonnes of flaming debris over the launch complex. An investigation discovered that the rocket’s onboard computer had issued a self-destruct command after detecting the structural failure of one of the solid rocket motors.
The first stage of the Delta II 7920-10C configuration which was used to launch NPP was an Extra-Extended Long Tank Thor with an RS-27A main engine and two LR-107 verniers, which ignited about two second ahead of the scheduled time of liftoff, T-0. A fraction of a second before T-0, six of the nine GEM-40 solid rocket motors igniteg, and at T-0 Delta 357 began its ascent towards orbit, flying on an azimuth of 196 degrees.
About sixty four seconds after launch, the six ground-lit solid rocket motors burnt out, and a second or two later the three air-lit motors ignited. The spent ground-lit motors remained attached to the first stage for about 22 seconds after burnout, in order to clear offshore oil rigs before they are jettisoned.
Separation of the solid rocket motors was around 86 seconds after liftoff, with the motors falling away in two groups of three. The air lit motors also burned for about 64 seconds, subsequently separating two minutes and 10.5 seconds after liftoff.
The first stage completed its burn 263.4 seconds after liftoff, with the main engine shutting down followed shortly afterwards by the two verniers. About eight seconds after main engine cutoff, or MECO, the first stage separated, and thirteen and a half seconds after MECO the second stage ignited to begin the first of four burns. The second stage was a Delta-K, powered by an AJ-10-118K engine.
The first burn lasted five minutes, 46.8 seconds, and just over four seconds into the burn, the payload fairing separated from around the satellites.
Following the end of the first burn, Delta 357 coasted for 41 minutes and 41.3 seconds before the second burn commenced. This burn lasted just 21.7 seconds, circularising the orbit for the deployment of NPP.
Spacecraft separation was seen 378 seconds after the burn ended; fifty eight minutes and forty five seconds after liftoff. The target orbit is a semi-major axis of 7201.15 kilometres, eccentricity of 0.00125, inclination of 97.703 degrees, and an argument of perigee of 69.21 degrees.
A separation burn was then made 33 minutes and 45 seconds later, putting distance between the upper stage and NPP ahead of CubeSat deployment. The separation burn lasted 39.2 seconds. Five minutes and 8.8 seconds after this burn completes, the first PPOD opened, releasing E1P-U2, AubieSat-1 and M-Cubed. The second PPOD was opened 98 seconds later, releasing the two DICE satellites, followed by the final PPOD 102 seconds after that, releasing RAX-2.
With all of its payloads deployed, Delta 357 made one more burn to deplete its remaining propellant. This lasted 31.9 seconds, and began around 13 minutes and 21 seconds after RAX-2 separates.
Originally used by the 75th Strategic Missile Squadron of the United States Air Force, and the Royal Air Force, for test-launching Thor missiles and training their crews, the first launch from the pad occurred on 17 September 1959.
The first orbital launch from the pad was made by a Thor-Agena in 1962, carrying a KH-4 satellite. The complex supported its first Delta launch in 1969 and its first Delta II launch in 1995.
The launch of NPP was conducted by United Launch Alliance, who operated the Delta II, Delta IV and Atlas V rockets, and provide launch services for the US government.
The next launch to be conducted by ULA will be that of the Mars Science Laboratory, which is currently scheduled for late November aboard an Atlas. The next Delta launch will be of a Delta IV in January, carrying a Wideband Global Satcom communications satellite.
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