Productivity and impact of space-based astronomical facilities

In 2001, 18 journals published about 1270 astronomical papers that reported and/or analyzed data gathered by space-based observatories and missions. These papers were cited 24,460 times in papers published in 2002 - 2004, an average of 19.26 citations per paper or 6.42 citations per paper per year ( sometimes called impact or impact factor). About 60 satellites, rockets, balloons, and planetary missions were represented, including six ground-based Cerenkov detectors for ultra-high energy gamma rays, because we didn't know where else to put them. Of these facilities, 21 provided the data for at least five papers, when credit was divided equally among all contributing facilities. We analyze here distributions of papers, citations, and impact factors among the facilities and among subject areas and compare the results with studies of optical and radio telescopes (Trimble et al. and Trimble & Zaich). Some similarities include the rarity of completely uncited papers (only 41 of 1274, or 3.2%) and the concentrations of the most highly cited papers toward popular topics, high-profile journals, and the most successful telescopes of the year. Some important differences arise because many space-based observatories have lifetimes shorter than the typical time required to think of an interesting astronomical observation, propose for it, get the data, write the paper and publish it ( including the fight with the referee), and have citations accumulate. The result is superstar status in citation numbers for XMM-Newton ( whose first-light package appeared in 2001) and in paper numbers for Chandra ( launched 5 months earlier), while aging satellites (RXTE, BeppoSAX, ASCA) and the archival-only ROSAT, ISO, IRAS, etc., were still important contributors, but with fewer papers and less highly cited papers. The impact factor of 6.42 for the totality of these gamma-ray, X-ray, ultraviolet, space infrared and optical, and planetary mission papers (6.42) was larger than the corresponding radio (4.52) and optical (5.47) numbers. Notice that HST is included with "optical" but Hipparcos with "space." A contemplated fourth paper will divide credit for papers and citations among every observatory of any sort that contributed to each published paper.