Kevin Fetter wrote: > Using this location I got for 8:19:56 UTC > 5.3530 S 22.0301 W and again 0 m above the WGS84 ellipsoid. Can't remember what model, it used for atmospheric refraction. > The iss is in the following state in relation to this site. > Azimuth (deg) Elevation (deg) Range (miles) > 65.603 9.955 839.205168 These compare to my resuls: Greatest transit of Venus 11210 8:19:44 8.4 65.9 906 -6.3542 -23.3779 8.3 0.2 11222 8:19:56 10.0 65.8 839 -5.3198 -22.0455 10.0 0.2 In this case, the transit spot is over the Atlantic, so sea-level certainly is accurate. Strangely, the computed values for azimuth, elevation, and range are in quite good agreement; Venus & the ISS are low in the ENE. However, my "shadow spot" is 2.68 miles north of yours! Atmospheric ray-bending would have the effect of moving the shadow in the direction of the ISS; effectively equivalent to increasing the observer's elevation above sea-level by 75 meters, in this case (which, given a range of 839 miles, would not be very significant). I'm currently using WGS72 constants in my program; however, the differences between it and WGS84 are quite small: 6378.135 km Earth radius in WGS72, and 2 meters more, in WGS84 (Earth flattening is 1:298.26 versus 1:298.2572 in WGS84). I decided to check CalSKY for this time, which currently appears to be using this identical TLE: ISS 73.0 44.5 27.5 0.5 d 234 1 25544U 98067A 04159.51921885 .00020000 00000-0 20000-3 0 9074 2 25544 51.6331 15.0248 0005532 209.7910 150.2937 15.68809969316800 Its results are in extremely close agreement with mine: Tuesday 8 June 2004 Observer Site WGS84: Lon: -22d02m43.8s Lat: -5d18m52.2s Alt: 3m All times in UT 8h19m56.15s ISS Crosses the disk of Venus. Separation: 0.00d Position Angle: 246.6d Angular Velocity: 10.4'/s. Transit duration: 0.09s Angular diameter: 13.7" size: 73.0m x 44.5m x 27.5m Satellite at az: 65.8d ENE h: 10.0d dist: 1351.2 km mag=14.4m Satellite apparently moves to direction 336.6° Centerline, Closest Point ->Map: Lon:+22d02m41s W Lat: -5d18m55s dist: 0.13 km az: 140.9d SE Path direction: 50.9d NE ground speed: 14.505 km/s width: 1.1 km max. duration: 0.1 s This made me suspicious, so I tried putting your values into CalSKY- it appears your values are quite close for a transit of (the center of) the Sun! I doubt that the MCC will update their ISS ephemeris page today; I hope they'll update it tomorrow. Until they do, one could use CalSKY to make comparisons (except that Arnold has apparently implemented GTOPO30 DEM, so CalSKY would use accurate elevation information- though the 3 meter elevation for the Altantic Ocean, here, is a little suspect ;-). Unfortunately, I don't have time to do any more myself, this morning. ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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