FYI Below is a message I archived from a discussion back in 1996 regarding seeing the shuttle in darkness. Bill Bard wtba@eci.esys.com >Date: 25 Jan 1996 15:54:25 -0500 >From: Bill Bard >Subject: Shuttle in Darkness Part 2 >Recently, Paul Maley (and someone else I think) reported seeing the >shuttle while it was in the earth's shadow. I think the estimated >magnitude was 7 and the shuttle was oriented with the payload bay towards >the earth. > >There are two possibilities that account for it being seen. One is that >moon light (instead of sun light) was illuminating the shuttle. The other >is that viewers on the ground were seeing the cargo bay lights. Regarding >the cargo bay lights, I found some info on the lights from a couple years >ago: > > There are 6 floodlights in the cargo bay. Each 160-watt light is rated > at 40 Lumens per watt. A seventh floodlight located on the forward > bulkhead is 200 watts and is rated at 40 Lumens per watt. The RMS > light is 150 watts and is rated at 12 Lumens per watt. > >With the cargo bay oriented towards the earth, I would assume that you >would then have 6 floodlights pointing towards you for a total brightness >of (6 * 160 W * 40 L) 38400 Lumens. Paul reported that 4 floodlights were >on so then the brightness should be 25600 Lumens. Any comments on how to >convert from Lumens to magnitude brightness? I think this can be done by comparing the Shuttle lights with the Sun. Our Sun has a visual magnitude of -26.8 and provides us with about 140,000 Lumen/qm. A Shuttle with four floodlights at a range of 100 km delivers 25600/(4*Pi*100000*100000) = 0.0000002037 Lumen/qm. Thus, the magnitude difference between the Shuttle and the Sun is 2.5 * log10(140000/0.0000002037) = 29.6 magnitudes. Shuttle magnitude is then -26.8 + 29.6 = 2.8. This calculation can be done for various ranges and gives: Range (km) Shuttle mag 100 2.8 200 4.3 300 5.2 400 5.8 600 6.7 800 7.3 1000 7.8 Paul Maley observed STS-72 on 1995 Jan 12 at about 11:34 UTC below Spica with mag 6.5 at a slant range of 300 km (elevation about 43 deg). Thus, this observation is easily explained by seeing parts of two floodlights! Other observations of Shuttles in darkness: 1993 Dec 04 Gary Emerson (STS-61) floodlit payload bay mag 8 at 1500 km (elevation approx. 17 deg) 1994 Sep 10 Russell Eberst 22:38:49 STS-64 mag 6.4 at 275 km (elevation 85 deg) 22:39:13 STS-64 mag 5.9 at 335 km (elevation 54 deg) 1994 Nov 03 Rainer Kracht 17:22:50 STS-66 mag 5 at 375 km (elevation 40 deg) By expressing magnitudes & ranges in Lumen one gets: 1993 Dec 04 mag 8 1500 km 47600 Lumen 1994 Sep 10 mag 6.4 275 km 7000 Lumen mag 5.9 335 km 16400 Lumen 1994 Nov 03 mag 5 375 km 47100 Lumen 1996 Jan 12 mag 6.5 300 km 7600 Lumen Observations by Gary Emerson and by me seem to be exceptionally bright, but can be explained with all floodlights turned on: 6 * 160 * 40 L + 200 * 40 L = 46400 Lumen. Rainer Kracht 1996 Jan 26 0412188960-0001@t-online.de R.Kracht@t-online.de ----------------------------------------------------------------- Unsubscribe from SeeSat-L by sending a message with 'unsubscribe' in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org http://www2.satellite.eu.org/seesat/seesatindex.html
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