Jonathan's Space Report No. 355 1998 Apr 11 Cambridge, MA ------------------------------------------------------------------------------- Shuttle and Mir --------------- Mir astronauts Solov'yov [sic: actually Musabaev] and Budarin carried out a 4h15m spacewalk on Apr 6 and splinted the dented Spektr solar panel. A problem with the station's attitude control system caused the spacewalk to be cut short. According to reports from Jim Oberg, the control center erroneously commanded the station to stop controlling its orientation, and, believing instead that fuel in the old VDU engine had run out, decided to tell the crew to return inside. Andy Thomas remained on board the station during the EVA. Another spacewalk was carried out on Apr 11. Hatch open was at 0955 UTC and closed at 1620 UTC. The old VDU engine was installed in 1992, attached to the Sofora boom sticking out from the Kvant module. Musabaev and Budarin dismounted it and jettisoned it into space. Two more spacewalks are planned to install the new VDU engine, currently mounted on the exterior of the Progress supply ship. STS-93/AXAF ----------- AXAF is the third of NASA's Great Observatories, after the Space Telescope (Hubble) and GRO (Compton). I expect to be giving regular updates on the progress of the new observatory, now scheduled for launch on Dec 3. The Advanced X-ray Astrophysics Facility satellite is now undergoing integration and test at prime contractor TRW/Redondo Beach. The AXAF satellite consists of a spacecraft module and a science instrument module (SIM) joined by a long tube called the Optical Bench Assembly (OBA). The spacecraft module carries deployable solar panels, the HRMA X-ray telescope, the ACA optical guide telescope, and the IPS integral propulsion system. The IPS has four bipropellant engine nozzles derived from TRW's DM-LAE apogee engine. AXAF will be launched attached to an IUS solid rocket, and will completely fill the Shuttle payload bay. The HRMA (High Resolution Mirror Assembly) telescope consists of four concentric grazing incidence mirrors. It's hard to persuade X-rays to change their direction, so you can't use the usual `normal incidence' reflective mirrors pointed at the sky, familiar in optical telescopes. Instead, somewhat bizzarely, you point your mirror at right angles to the incoming X-rays, and they glance off at `grazing incidence', changing direction by only a degree or so. This is enough to let you focus the X-rays into a picture. The resulting telescope mirror is almost cylindrical, which lets you put progressively smaller mirrors one inside the other. The peer review of the first AXAF observing proposals was carried out last week. The first year's observing was heavily oversubscribed, with over 700 proposals submitted. Results will be announced next month. Satellite Names --------------- Since the late 1970s, NASA has made a practice of naming its larger satellites, usually after a famous dead scientist. Other space agencies have named their satellites after flowers, minerals, elementary particles, mythological characters, or astronomical objects. I've tried to collect together a list of these satellite names at http://hea-www.harvard.edu/~jcm/space/misc/names.html Corrections and additions are welcome. Recent Launches --------------- Seven more Iridium satellites were launched on Apr 7. A Krunichev three-stage Proton-K launch vehicle placed the Iridium cluster and an Energiya commercial Blok DM2 stage (related to the domestic 17S40 Blok DM-5 variant) in low parking orbit. The DM2 then fired twice to enter the deployment orbit and dispensed the seven satellites, which will use their own propulsion units to reach operational altitude. The DM2 stage then fired again to deorbit itself, to avoid creating space debris. Iridium constellation status: The constellation is now filling up the last of the six orbital planes. In addition, two satellites (SV18 and SV38) which had been in engineering orbit for several months raised their altitude to the operational orbit in early April. The operational orbit is 776 x 779 km x 86.4 deg, while the engineering orbit is 765 x 771 km x 86.4 deg. A total of 45 satellites are in operational orbit, a further 14 are on their way there from the initial deployment orbit, two satellites are dead, and four are in engineering orbit, for a total of 65 Iridiums launched to date. Plane 1: Operational: [0] Raising orbits: SV62,63,64,65,66,67,68 Plane 2: Operational: [9] SV22,23,24,25,26,45,46,47,49 Engineering orbit: SV48 (since Feb) Plane 3: Operational: [6] SV28,29,30,31,32,33 Raising orbits: SV55,57,58,59,60 Failed in deployment orbit: SV27 Plane 4: Operational: [10] SV04,06,07,08,19,34,35,36,37,51 Raising orbits: SV61 Engineering orbit: SV05 (since Jan) Plane 5: Operational: [10] SV09,10,12,13,14,16,50,53,54,56 Raising orbits: SV52 Engineering orbit: SV11 (since Sep) Plane 6: Operational: [10] SV15,17,18,20,38,39,40,41,43,44 Engineering orbit: SV42 (since Dec) Failed in deployment orbit: SV21 In my comments on sun-synchronous orbits last week, several folks pointed out some loose statements on my part. When I suggested that orbital planes 'normally' stay fixed, I meant when in orbit around a perfect Newtonian point mass. Any inclined Earth satellite will have an orbital plane precession due to the Earth's lack of spherical symmetry (and to much smaller degree due to GR effects). The upper inclination limit of around 110 degrees corresponds to an upper altitude limit of around a couple thousand km, reflecting the use of sun-synchronous orbits in historical practice. Of course, sun-synchronous orbits at even higher altitudes and inclinations are perfectly possible, they just haven't tended to be used up to now. Table of Recent Launches ------------------------ Date UT Name Launch Vehicle Site Mission INTL. DES. Mar 14 2246 Progress M-38 Soyuz-U Baykonur LC1 Cargo 15A Mar 16 2132 UHF F/O F8 Atlas II Canaveral SLC36A Comsat 16A Mar 24 0146 SPOT 4 Ariane 40 Kourou ELA2 Imaging 17A Mar 25 1701 Iridium 51 ) CZ-2C/SD Taiyuan Comsat 18A Iridium 61 ) Comsat 18B Mar 30 0602 Iridium 55 Delta 7920 Vandenberg SLC2 Comsat 19A Iridium 57 Comsat 19B Iridium 58 Comsat 19C Iridium 59 Comsat 19D Iridium 60 Comsat 19E Apr 2 0242 TRACE Pegasus XL Vandenberg Solar obs. 20A Apr 7 0213 Iridium 62 Proton-K/DM2 Baykonur Comsat 21A Iridium 63 Comsat 21B Iridium 64 Comsat 21C Iridium 65 Comsat 21D Iridium 66 Comsat 21E Iridium 67 Comsat 21F Iridium 68 Comsat 21G Current Shuttle Processing Status __________________________________ Orbiters Location Mission Launch Due OV-102 Columbia LC39B STS-90 Apr 16 OV-103 Discovery OPF Bay 2 STS-91 May 28 OV-104 Atlantis Palmdale OMDP OV-105 Endeavour OPF Bay 1 STS-88 Sep 17? MLP/SRB/ET/OV stacks MLP1/RSRM66/ET-96 VAB Bay 1 STS-91 MLP2/RSRM65/ET-91/OV-102 LC39B STS-90 MLP3/ .-------------------------------------------------------------------------. | Jonathan McDowell | phone : (617) 495-7176 | | Harvard-Smithsonian Center for | | | Astrophysics | | | 60 Garden St, MS6 | | | Cambridge MA 02138 | inter : jcm@urania.harvard.edu | | USA | jmcdowell@cfa.harvard.edu | | | | JSR: http://hea-www.harvard.edu/~jcm/space/jsr/jsr.html | | Back issues: ftp://sao-ftp.harvard.edu/pub/jcm/space/news/news.* | | Subscribe/unsub: mail majordomo@head-cfa.harvard.edu, (un)subscribe jsr | '-------------------------------------------------------------------------'