This paper gives a description of the mission design, launch, orbit, and navigation results for the Spitzer space telescope mission. The Spitzer telescope was launched by the Delta II Heavy launch vehicle into a heliocentric Earth trailing orbit. This orbit is flown for the first time and will be used by several future astronomical missions such as Kepler, SIM, and LISA. This paper describes the launch strategy for a winter versus a summer launch and how it affects communications. It also describes how the solar orbit affects the design and operations of the Observatory. It describes the actual launch timeline, launch vehicle flight performance, and the long term behavior of the as flown orbit. It also provides the orbit knowledge from in-flight navigation data.
The Space Infrared Telescope Facility (SIRTF) observatory is an 85-cm telescope with three cryogenically cooled instruments. Following launch, the observatory will be initialized and commissioned for routine operations during a sixty-day period called In-Orbit Checkout (IOC), and a subsequent thirty-day period called Science Verification (SV). The emphasis for the IOC phase is to bring the observatory on-line safety and expeditiously, verify functionality of the instruments, telescope, and spacecraft, and demonstrate that the facility meets level-1 requirements. The emphasis of the SV phase is to characterize the observatory in-orbit performance, demonstrate capability for autonomous operations, conduct early release observations, and exercise the ground systems software, processes, and staffing sufficiently to commission the facility for routine operations.
The design of the IOC/SV phases is dominated by two unique features of the SIRTF mission: the solar orbit that affects the thermal design and the communications strategy, and the warm launch architecture whereby the telescope is outside the cryostat and radiatively cools in deep space. The key challenges of SIRTF are in the areas of optical, cryogenic, and pointing control performance, which have dependencies on the performance of the three instruments, and vice versa. In addition, the mission and science operations teams must face the challenge of operating a new space observatory and safely establishing autonomous operations in a very short time. This paper describes a nominal mission plan that progressively establishes SIRTF capabilities during the IOC/SV phases, taking into consideration thermal, cryogenic, optical, communications, celestial mechanics, and operational designs and constraints.
The instruments of the Space Infrared Telescope Facility (SIRTF) are cooled directly by liquid helium, while the optical system is cooled by helium vapor. The greater the power dissipation into the liquid helium, the more vapor is produced, and the colder the telescope. Observations at shorter wavelengths do not require telescope temperatures as low as those required at shorter wavelengths. By taking advantage of this, it may be possible to extend the helium and mission lifetime by 10% or even 20%
The Space Infrared Telescope Facility (SIRTF) will explore the birth and evolution of the Universe with unprecedented sensitivity. SIRTF will be the first mission to combine the high sensitivity achievable from a cryogenic space telescope with the imaging and spectroscopic power of the new generation of infrared detector arrays. The scientific capabilities of this combination are so great that SIRTF was designated the highest priority major mission for all of U.S. astronomy in the 1990s. The astronomical community will use SIRTF to explore the infrared universe with a depth and precision complementary to that achieved by NASA's other great observatories -- the Hubble Space Telescope (HST), the Advanced X-ray Astrophysics Facility (AXAF), and the Compton Gamma Ray Observatory (GRO) in their respective spectral bands. The launch of SIRTF in 2001 will permit contemporaneous observations with HST to study forefront problems of astrophysics. This paper provides a comprehensive review of the SIRTF program -- the science, the mission design, the facility, the instruments, and the implementation approach. Emphasis is placed on those features of the program including the use of a solar (heliocentric) orbit and the adoption of a novel warm-launch cryogenic architecture -- which will allow us to realize the great scientific potential of SIRTF in a resource- constrained environment.
This paper describes a new mission concept for the Space Infrared Telescope Facility (SIRTF). In this new concept, SIRTF is launched with just enough energy to escape Earth's gravity. This trajectory is equivalent to a 1 astronomical unit (AU) solar orbit with a small drift rate of about 0.1 AU per year away from the Earth. The new concept uses an Atlas IIAS class launch vehicle to place an 85 cm diameter telescope with a 3 year minimum cryogenic lifetime into a solar orbit. There are many advantages of the solar orbit over an Earth orbit. The spacecraft design can be simplified. Communications and operations can be geared to a 24 hour day, although a directional antenna is needed because of the increasing distance from Earth. Additional advantages include the elimination os the need for Earth/Moon avoidance requirements and the ability to view large portions of the sky continuously for weeks or even months.
The Space Infrared Telescope Facility (SIRTF) is the fourth in NASA's series of Great Observatories. It will feature a one-meter class cryogenically cooled telescope. It is planned for a NASA fiscal start for the development phase in 1994 with a launch in about 2001. The launch vehicle will be the new upgraded Titan IV with a Centaur upper stage. The operational orbit will be circular at an altitude of about 100,000 km. The planned mission lifetime is 5 years. This paper addresses the rationale in the selection of the high altitude orbit, the performance of the launch vehicle in delivering the observatory to orbit, other orbit options, and the planned observational modes and capabilities of the observatory. The paper will also address the viewing geometry and viewing constraints affecting science observation, telescope aperture shade design, and spacecraft solar-panel and communication design.