Esa Bulletin May 1996 [antikvár]

gj-esa bulletin 86____The First Results from ISOM.F. KesslerISO Science Operations, ESA Space Science Department, Villafranca, SpainThis article gives a summary of the early in-orbit performance of the Agency's recently launched Infrared Space Observatory (ISO) spacecraft and its Instruments and presents some of the initial scientific results.Chronology of ISO Events17 Nov. 1995 Launch from Kourou at 02.20 CET19 Nov. 1995 Perigee-raising manoeuvre (from 500 to 1000 km)21 Nov. 1995 Start of 'Satellite Commissioning Phase'24 Nov. 1995 Apogee-lowering manoeuvre - operational orbit attained27Nov. 1995 Ejection of 'cryo-cover'28Nov. 1995 First light with ISOCAM - M 5129Nov. 1995 First light with ISOPHOT - Gamma Draconls30Nov. 1995 First light with LWS - S 10601 Dec. 1995 First light with SWS - Gamma Draconis08Dec. 1995 End of 'Satellite Commissioning Phase'09Dec. 1995 Start of 'Performance Verification Phase'03Feb. 1996 End of 'Performance Verification Phase'04Feb. 1996 Start of 'Routine Operations'Figure 1. Lift-off of the Ariane-44P carrying ISO into orbitIntroductionThe Agency's Infrared Space Observatory (ISO) was given a perfect launch by an Ariane-44P vehicle (Fig. 1) Into its planned elliptical transfer orbit, with lift-off from Kourou occurring at 02.20 CET on 17 November 1996.The first 21 days after launch were devoted to the so-called 'Satellite Commissioning Phase'. During this period, the operational orbit was attained, the cover that had closed off the cryostat on the ground was ejected, the spacecraft was shown to be In excellent condition, 'first light' for all instruments was achieved, engineering checks were successfully completed on all four scientific Instruments, and the Integrated ground segment was validated.The next 56 days (I.e. from 8 December to 3 February) were devoted to the so-called 'Performance Verification Phase', during which a detailed assessment of the In-flight performance of the scientific instruments was made, their core calibrations established, and planned operating modes validated. The data acquired during this period are being used to verify the pipeline data processing and Its products.Table 1 summarises the main features of the ISO Instruments. A set of five articles in ESA Bulletin No. 84 (November 1995) gave a complete overview of the ISO programme.In-orbit performanceAriane Injected ISO Into a transfer orbit with a perigee of 500 km and an apogee of 71 600 km. The operational orbit (perigee of 1000 km and apogee 70 600 km) was achieved, as planned, with three uses of the hydrazine reaction-control system, on18November (test burn and rehearsal), on19November (perigee-raising manoeuvre) and on 24 November (apogee-lowering manoeuvre). An estimated 50 kg of hydrazine remains on-board, whereas only about 12 kg are needed for the planned ISO operations.