been flown since then in 1984 and 1991, although only the last flight involved a release of the platform. SPAS is essentially made up of the same basic structural elements as Eureca and the USS and is capable of carrying up to 900 kg of pay load. The basic SPAS is currently scheduled to fly once more in 1993 as a follow-up to the US SDIO SPAS mission flown in 1991. After that. Germany has developed a larger and more capable variant of the SPAS platform, designated Astro-SPAS. The Astro-SPAS program is a cooperative effort with the US where DARA is providing the spacecraft and integration services and NASA is providing the launch and various launch support services. Both nations are providing the science pay loads for upcoming missions. Currently, Astro- SPAS is scheduled to fly on STS-59 in early 1993, and on STS-66 in 1994. In addition, at least 2 more flights are planned thereafter. The first mission is dedicated to UV astronomical observations and the second is dedicated to atmospheric measurements. The Astro-SPAS platform is detailed in Figure 3.4-1. The platform has a number of features that would be to the advantage of the Powersat demonstrator. In particular, [17] • It exists, • Qualified for Shuttle operations, • Standard payload interface rings, • Large pay load volume of 3.9 m x 1.2 m in diameter, • Maximum pay load mass of 1,800 kg, • High pointing precision of better than 30 arc seconds with respect to a moving target, • High on-board data storage capacity of 50 Gigabits, • High battery power for experiments of up to 50 kWh.
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