ULA Delta II launches with the SAC-D spacecraft

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The United Launch Alliance (ULA) have launched their Delta II rocket to loft the SAC-D spacecraft into orbit for the Argentine space agency, CONAE, on Friday. Launch occurred at the start of a five minute window opening at 14:20:13 UTC (07:20 local time), lifting off from Space Launch Complex 2W at the Vandenberg Air Force Base in California.

Delta II Launch Overview:

SAC-D, or “Satelite de Aplicaciones Cientificas D”, is the fourth in a series of Argentine scientific satellites, the first of which, SAC-B, was launched in November 1996. SAC-B was intended to study solar flares, x-rays and gamma ray bursts.

Launched aboard a Pegasus-XL rocket along with NASA’s HETE-1 satellite, both spacecraft were lost after the rocket failed to deploy them upon reaching orbit. Despite operating for ten hours before running out of power, SAC-B was unable to conduct any scientific research, and reentered the atmosphere still attached to HETE-1 and the Pegasus upper stage on 7 April 2002.

The next satellite, SAC-A, was deployed from Space Shuttle Endeavour on 14 December 1998 during the STS-88 mission; the first Space Shuttle mission to the International Space Station. It carried five experiments, primarily intended to demonstrate technology for future missions.

The primary experiment was to demonstrate the use of GPS satellites to track it in orbit. It also carried a CCD camera for Earth imaging, a magnetometer to study the magnetic field of the Earth, some experimental solar cells, and an instrument designed to track whales. The satellite remained in orbit until 25 October 1999.

The third satellite, SAC-C, was launched on 21 November 2000, atop a Delta II flying from the same launch pad and in the same configuration as will be used for the launch of SAC-D. It was a secondary payload on the rocket which launched NASA’s Earth Observing 1 (EO-1) spacecraft.

SAC-C’s primary mission was to conduct multispectral imaging over Argentina, augmented by medium and high-resolution cameras. It also carried experiments to study the effects of the Sun upon the Earth’s magnetic field, a helium magnetometer, another payload to track whales, as well as several technology demonstration payloads. The satellite is currently still in orbit.

SAC-D carries nine instruments. Its primary experiment is Aquarius, which will be operated by NASA. Aquarius is designed to study the salinity of the Earth’s oceans by means of three radiometers and a radar scatterometer. It has a mass of 320 kilograms, and is designed to operate for three years.

Five CONAE experiments are aboard the spacecraft. The Microwave Radiometer, MWR, will provide measurements of the wind, precipitation and sea ice conditions, and the amount of water vapour in the air; data which will be used to supplement that collected by Aquarius.

The New Infrared Scanner Technology experiment, or NIRST, is an instrument which will measure temperatures on the surface of the Earth. It will be operated jointly by CONAE and the Canadian Space Agency, and will primarily be used to detect fires, and to record sea temperatures in support of Aquarius.

The High Sensitivity Camera (HSC) will be used to image aurorae, fires, and the light emitted from cities. A Data Collection System (DCS) payload aboard the satellite will be used to collect and relay data from ground-based weather stations. The fifth CONAE experiment is the Technology Demonstration Package will be used to demonstrate whether a GPS receiver can be used to determine the location, velocity and rotation rate of the spacecraft.

The Radio Occultation Sounder for Atmosphere (ROSA) instrument will be operated by the Italian space agency, ASI. It will use GPS occultation measure the pressure, temperature and humidity of the atmosphere. Finally, SAC-D carries two instruments for the French Space Agency, CNES. These are ICARE-NG and SODAD, collectively known as CARMEN 1.

ICARE-NG is a 2.38 kilogram instrument which will be used to study electron and proton flux in space, and their effects upon instruments. Another ICARE-NG payload was launched as CARMEN 2, aboard the Jason-2 satellite in June 2008. SODAD consists of three detectors which will be used to study orbital debris and micrometeorites. A fourth detector, MEDET, was launched aboard Space Shuttle Atlantis during the STS-122 mission in 2008, and was subsequently installed aboard the International Space Station.

The Delta II which was used for Friday’s launch was a Delta 354, which was the 149th flight of the Delta II. The rocket flew in the 7320-10C configuration, using three GEM-40 solid rocket motors to augment the first stage – an Extra-Extended Long Tank Thor.

The second stage used was a Delta-K, while the rocket had no third stage. SAC-D was encapsulated in a composite payload fairing with a diameter of three metres (10 feet), which protected it from atmospheric pressures acting upon the rocket during ascent.

The first stage was fuelled by RP-1 propellant and liquid oxygen oxidiser, which powered a single RS-27A main engine, and two LR-101-AN-11 vernier engines used to control the rocket’s attitude. The Delta-K was powered by an AJ-10-118K engine, which burns Aerozine-50 propellant and dinitrogen tetroxide oxidiser. The AJ-10-118K is a derivative of the engine used on the second stage of the Vanguard rocket, which was used for the United States’ first attempt to orbit a satellite in 1957.

Three hours minutes before launch, the terminal countdown began, and an evacuation klaxon was sounded. Over the next fifty minutes, the Missile Hazard Area was cleared. About two minutes into the countdown, activation of the Redundant Inertial Flight Control Assembly (RIFCA) began, a process lasting a little over seventy minutes. Shortly after this started, pressurisation of helium and nitrogen tanks aboard both stages began.

Pressurisation of the first stage tanks took around fifteen minutes, whilst pressurisation of the second stage tanks lasted for a little under seventy minutes.

Twenty minutes into the countdown, and 160 minutes before launch, the countdown reached T-130 minutes and fuelling of the first stage began. In the event of high winds at the launch site, this is sometimes conducted before the start of the terminal countdown, in order to increase the mass and lower the centre of gravity of the rocket before the retraction of the Mobile Service Tower (MST), in order to make the rocket more stable. Either way, fuelling lasts thirty five minutes, as was the case for Friday’s preparations.

Between 130 and 105 minutes before launch, testing of the rocket’s C-band beacon was conducted. About 105 minutes before launch the air conditioning system was set to high heat mode, and at around the same time loading of liquid oxygen into the first stage tank began. Liquid Oxygen loading took  just under 40 minutes, concluding around 67 minutes before launch.

Also around 67 minutes before launch the command carrier is activated, and for the next ten minutes, tests were performed upon the command receivers. Then the first stage hydraulics system was activated, and slew checks were performed on the engines for ten minutes. Five minutes of radio frequency link checks followed.

Forty five minutes before launch, the countdown entered a planned twenty minute hold at T-15 minutes. At the end of this hold the helium and nitrogen tanks were topped off. Twenty minutes before launch the fuel tank was pressurised, following which status checks were conducted.

Fourteen minutes before launch the countdown enters a ten minute hold, final checks were conducted. Once the hold ends, the rocket and spacecraft were transferred to internal power, armed, and a final go was given from spacecraft controllers.

Two seconds before launch, the first stage engines ignited. At T-0 seconds, the solid rocket motors also ignited, and Delta 354 began to climb away from its launch pad towards orbit, along an azimuth of 169 degrees.

The rocket passed through the sound barrier 36.1 seconds after launch, and shortly afterwards it experienced the area of maximum dynamic pressure, Max-Q. Sixty four seconds into the flight the solid rocket motors burnt out, however they remained attached for another thirty five seconds to avoid the possibility that they could hit oil rigs off the coast of California.

Four minutes and 24.2 seconds after lifting off, Main Engine Cutoff, or MECO, occurred, followed shortly afterwards by Vernier Engine Cutoff, or VECO. These events marked the end of the first stage burn, the stage having expended all of its fuel. First stage separation from the second stage occurred eight seconds after MECO, with the second stage engine igniting five and a half seconds after staging.

The first burn of the second stage lasted 398.4 seconds, concluding 11 minutes and 16.1 seconds after launch. About 12.3 seconds after the start of the burn, the payload fairing separated from the rocket, with the exact time of separation being determined by sensors monitoring whether the rate of free molecular heating has dropped below 1,135 watts per square metre (0.1 British thermal units per square foot per second).

Following the completion of the first burn, Delta 354 entered a coast phase lasting 41 minutes and 3.6 seconds, before the AJ-10 engine ignited again for its second burn. This burn lasted only 12.3 seconds, in order to circularise Delta 354’s orbit. Four minutes and ten seconds after the conclusion of the burn, and 56 minutes and 42 seconds after lifting off, the SAC-D satellite separated from the upper stage of Delta 354.

At spacecraft separation, SAC-D’s orbit is expected to have a semi-major axis of 7038.099 kilometres with eccentricity of 0.0012, giving it an apogee of 679.1 km (422 miles) and a perigee of 662.2 km (411.5 miles). The orbit will have an inclination of 98.08 degrees to the equator.

After spacecraft separation, the second stage usually performs a helium blowdown manoeuvre to move away from the satellite, followed by two further burns; one to lower the upper stage’s orbital perigee, and one to deplete any remaining fuel. Whilst they are likely to occur, United Launch Alliance has not confirmed whether these manoeuvres will be performed during the flight of Delta 354.

Delta 354 launched from the West pad of Space Launch Complex 2 (SLC-2W) at Vandenberg Air Force Base. Originally built as Launch Complex 75-1-2 in the 1950s, SLC-2W and was used by the 75th Strategic Missile Squadron of the United States Air Force and the Royal Air Force, to conduct test and training launches of Thor missiles. From 1962 Thor-Agena rockets began making orbital launches from the complex, and in 1969 Delta launches from the complex started. In 1995 the Delta II made its first launch from the complex 1995.

The launch of Delta 354 marked the 31st and final flight of the Delta II Med-Lite series, developed in the late 1990s to accommodate payloads which did not require a full-capacity Delta II with nine solid rocket motors. The Med-Lite series consisted of the 7320-series and the 7420-series, with three and four solid rocket motors respectively. The 7420-series made eighteen flights, concluding with COSMO-4 last October, whilst the launch of SAC-D is the thirteenth launch of a 7320-series rocket.

The 7300-series Delta II first flew on 24 October 1998, carrying the Deep Space 1 and SEDSat spacecraft. This was one of three launches in the 7326 configuration, featuring a Star-37FM upper stage. The other two 7326 launches were those of IMAGE in March 2000, and Genesis in August 2001. The 7320 configuration, with no upper stage, has been used for all other launches, beginning with FUSE on 24 June 1999. Its most recent launch was on 14 December 2009, with the launch of WISE.

The launch of SAC-D marked the 149th flight of the Delta II, with two more launches scheduled. Components to build five Delta II Heavy rockets exist; however they have not yet been assembled or assigned to specific payloads. NASA has reportedly held talks with United Launch Alliance about restoring the Delta II to its Launch Services Contract, and it has been rumoured that NASA has been considering assigning the launch the OCO-2 satellite to a Delta II, after the Taurus-XL rocket which is currently scheduled to launch it experienced two consecutive failures.

The next scheduled Delta II launch is currently expected to occur on 8 September, when the final flight of a Delta II from Cape Canaveral will orbit NASA’s GRAIL spacecraft on a mission to the Moon. Prior to that, next month a Delta IV will launch a Global Positioning System satellite from Cape Canaveral.

(Images: ULA)

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