The NASA Glenn (formerly Lewis) Research Center was responsible for providing the
launch services for the Cassini
mission to Saturn. On Wednesday, October 15, 1997 at 4:43 a.m. EDT, a
Titan IV-B launch vehicle with a Centaur high-energy upper stage lifted Cassini out of Earth’s gravitational pull, placed it into Earth orbit, and sent it on the first leg of its long journey. The Cassini spacecraft was inserted onto its trans-Venus trajectory with the expected high precision generally associated with the Centaur upper stage. The Glenn effort was accomplished in close cooperation with the United States Air Force (USAF) which manages the Titan IV-B program,
and the NASA Jet Propulsion Laboratory which manages the spacecraft
and the overall Cassini program.
Cassini will go into orbit around Saturn and study its atmosphere, magnetic fields, rings, and icy moons. The Huygens probe, supplied by the European Space Agency (ESA), will scrutinize the clouds, atmosphere, and surface of Saturn's moon Titan. The Cassini spacecraft is also carrying an additional special payload -- a compact disk with the digitized signatures of about a million school children.
This complex mission has been taken on by a talented team of scientists, engineers, technicians and other personnel from Cassini’s Government and industry partners. NASA has the ultimate responsibility for Cassini’s success, including the launch service. The Glenn Research Center was responsible for integration of the spacecraft with the launch vehicle and the design of mission-unique hardware and software modifications necessary for that integration. To support these tasks, NASA Glenn contracted with the Lockheed Martin Corporation. Under a memorandum of agreement with NASA, the USAF was responsible for procuring the basic launch vehicle and conduct of launch operations. Lockheed Martin was the prime contractor to the USAF for the Titan IV-B program and its Centaur upper stage.
NASA Glenn was also involved in the 1990 jettison testing of the 86-foot tall, 16-foot diameter Titan IV payload fairing under a cooperative agreement between the USAF, the Martin Marietta Company (now Lockheed Martin Corporation), and NASA. The tests were conducted at NASA Glenn's Plum Brook Station in the Space Power Facility (SPF), the world's largest space environment simulation chamber. This fairing, the largest payload fairing ever tested in a vacuum chamber, had internal payload space dimensions approximating the space shuttle orbiter bay.
Building on a strong working relationship, NASA Glenn and the USAF closely coordinated the basic launch vehicle production, definition of launch support requirements, and verification that all mission requirements were met. In addition, Glenn participated in all Air Force vehicle production reviews and launch processing coordination meetings and reviews. Glenn also participated in the actual launch operations, including the prelaunch countdown.
For Titan IV missions, independent verification and validation analyses are normally conducted to assure mission success. Coupled loads, spacecraft dynamic testing, software, vehicle guidance and control, mission design, separation dynamics, and flight performance must all be assessed. Although these analyses are normally performed by a separate contractor, NASA Glenn performed these analyses for the Cassini mission as part of its integration responsibility and to take advantage of the extensive experience and specialized expertise available at Glenn. This was important because Cassini is one of the heaviest (over 5600 kg, or 12,000 lb) and most complex planetary spacecraft ever made.
The Titan IV-B is the Nation’s largest and most powerful expendable launch vehicle. It also is the Nation’s newest model heavy-lift launch vehicle. This mammoth rocket is as tall as a 20-story building and weighs about 940,000 kg (2 million lb) with the solid rocket boosters and fuel.
During the Cassini launch, members of the NASA Glenn team, including Center Director (1994-2003) Donald Campbell, monitored the flight of the spacecraft through completion of the Centaur separation including contamination and collision avoidance maneuvers. After the three Titan IV stages had burned out, the Centaur separated from the booster vehicle and burned for approximately two minutes, placing the spacecraft in a "park" orbit. After 20 minutes in orbit, the Centaur fired for the last time and launched Cassini out of Earth orbit and onto its trajectory toward Venus. The majority of Cassini’s 7-year trip to Saturn is an unpowered coast through space.
Every launch opportunity to Saturn has a single day that provides the best performance. There is no guarantee, however, that the launch vehicle will be able to launch that day due to bad weather at the launch pad or a problem with the launch vehicle or spacecraft. To increase the chances at being able to launch, a series of days called a launch period, or launch window, are planned for launch availability. Most planetary missions, like Cassini, design for a launch period of 30 days.
The launch period for this mission opened on October 6, 1997, and extended through November 4, 1997, providing a primary 30-day
launch window. The opening and close of the launch period were chosen such that the launch vehicle's capabilities are not
exceeded, and the mission performance and operational requirements are met. The launch period could have been extended beyond
the nominal launch period to November 15, 1997, to increase the chances of mission success, although the scientific return
would have been degraded somewhat since some extra propellant would have been required just to get to Saturn.
Since 1962, NASA Glenn has been responsible for all intermediate and large class payload launches on expendable (unmanned) rockets by NASA -- a total of 119 launches. Until the advent of the space shuttle program, this responsibility included all U.S. launches to the planets. NASA Glenn is proud to be a vital part of the Cassini mission.
Fact Sheet also available: A Big Boost for Cassini: NASA Glenn Efforts Launch Cassini Toward Saturn [HTML] or [427 KB PDF]
NASA Glenn's Communications Technology Division contributed to the spacecraft by developing a 32 GHz traveling wave tube (TWT) and it's power supply, together called a traveling wave tube amplifier (TWTA), and providing flight hardware to the Cassini mission. TWTs are an advanced type of vacuum tube amplifier that offers lighter weight, higher reliability, and higher efficiency than solid-state amplifiers at high RF power levels (>10W). Glenn also provided technical support to JPL in the development of the 8.4 GHz traveling wave tubes and their power supply. The 8.4 GHz TWTAs provide the radio link to earth. The 32 GHz TWTA will be used, along with the 8.4 GHz TWTAs in a gravitational wave experiment, as well as in radio science experiments.
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