will be operated for 5 years, with enough fuel to allow an extension to 10 years. A second infrared telescope, SOFIA, operates out of a Boeing 747 airplane and is due to begin full operations in 2 years. The only other U.S.-led space astrophysics missions currently under construction are the Explorer X-ray missions NuSTAR (to be launched in 2012) and GEMS (scheduled for 2014). There is significant U.S. participation via the Explorer program in the Japanese-led X-ray telescope Astro-H, scheduled for launch in 2014.
NASA also has a balloon program and a suborbital rocket program. Both are highly effective in terms of the scientific results they produce and the fast turnaround they allow, with typically less than 3 years between concept development and flight.5
NASA also operates the Infrared Telescope Facility (IRTF) in Hawaii and participates as a one-sixth partner in the W.M. Keck Observatory, also in Hawaii. These NASA programs recognize the importance of optical-infrared data from ground-based telescopes in planning and preparing for, and in interpreting the results from, its space missions—in astrophysics at gamma-ray through mid-infrared wavelengths and in planetary science from numerous in situ locations around the solar system.
NASA holds regular senior reviews to decide which missions to terminate, and it is anticipated that every one of its currently orbiting space telescopes, including Hubble (which needs an expensive de-orbiting mission), will cease operations before the end of the decade. SOFIA, which has operations costs of $70 million per year, will be subject to a senior review after 5 years of operations. Thus, with the possible exception of JWST and SOFIA, none of the missions operating or started today are expected to be operational at the end of the decade.
Summarizing the cost and the frequency of appearance of new capabilities, Figure 6.3 shows NASA missions operating during the past two decades and expected during 2010-2020. The chart illustrates the shift from a mix of mission sizes in the 1990s, to no flagships but a number of smaller missions launched in 2000-2010, to one or possibly two flagships and many fewer smaller missions projected for 2010-2020. Part of this evolution is a result of growing mission complexity. However, the percentage of the NASA Astrophysics Division budget being spent on large missions has been relatively constant for most of the past two decades. The overall lack of mission opportunities is due to the combination of a decrease in the available budget and the increase in expenditures on missions currently operating. The number of missions in operation is large compared to the past several decades.