Great Observatories Program - Successors To GO Instruments

Successors To GO Instruments

• James Webb Space Telescope (JWST) — the JWST, previously known as the NGST (Next Generation Space Telescope) is projected to replace Hubble (HST) around 2017. Its segmented, deployable mirror will be over twice as large, increasing angular resolution noticeably, and sensitivity dramatically. Unlike Hubble, JWST will observe in the infrared, in order to penetrate dust at cosmological distances. This means it will continue some Spitzer capabilities, while some Hubble capabilities will be lost. New advances in ground telescopes will take over some visible observations, but fewer in ultraviolet.

• The Fermi Gamma-ray Space Telescope, formerly GLAST, the Gamma Ray Large Area Space Telescope, is a follow-on to Compton launched on June 11, 2008. GLAST is more narrowly defined, and much smaller; it will carry only one main instrument and a secondary experiment. Other missions, such as HETE-2, launched in 2000, and Swift, launched in 2004, will complement GLAST. The Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), launched in 2002, observes in some Compton and Chandra wavelengths, but is pointed at the Sun at all times. Occasionally it observes high-energy objects which happen to be in the view around the Sun.
• Another large, high-energy observatory is INTEGRAL, Europe's INTErnational Gamma Ray Astrophysics Laboratory, launched in 2002. It observes in similar frequencies to Compton. But INTEGRAL uses a fundamentally different telescope technology, coded-aperture masks. Thus, its capabilities are complementary to Compton and GLAST, not a direct replacement.
• Spitzer has no direct successor planned. However, JWST will exceed its performance in near-infrared, and the European Space Agency's Herschel Space Observatory, launched in 2009, will exceed it in the far-infrared. The SOFIA (Stratospheric Observatory For Infrared Astronomy) airborne platform will observe in near- and mid-infrared. SOFIA will have a larger aperture than Spitzer, but at lower relative sensitivities in restricted duty cycles. Also, smaller space missions will perform specialized infrared observations.

• Constellation-X — A mission to perform extremely sensitive x-ray observations, beginning around 2016. This is not a direct replacement for Chandra; Chandra is optimized for high angular resolution. Constellation-X is more of a follow-on to the XMM-Newton mission, which trades resolution for sensitivity. Constellation-X may be several times to several dozen times more sensitive than Chandra. It will also extend further into the hard x-ray regions, giving it some abilities of Compton.

Note that none of these missions are designed for Shuttle launch, or manned servicing. Most are in orbits beyond the Shuttle's capability, to allow new observing modes.