Hi All, I observed a nice solar array flare from Iridium 30 last night (Tuesday, June 12th) at 21:02:40 PDT from Newport Coast, CA. Peak brightness was a little brighter than Vega -- perhaps -0.5. My Iridium solar array glint model was predicting about +0.0, which is well within the expected error of +/- 2 visual magnitudes. I feel I'm ready to release the current version of the program so as to allow a wider data-collecting audience for these solar array flares. More people watching means more observations can be reported, allowing me to improve on the preliminary magnitude curve that I've put in IRIDFLAR. I will be sending the code to Ed Cannon and Mike McCants later today so that they can host it. If anyone else wants to host a copy of the program on their website, please contact me. I want to emphasize that we will never be able to predict solar array flare magnitudes as accurately as the regular MMA flares since the pointing requirements for the articulating solar arrays are far less stringent than those for the MMAs (which are tied to the orientation of the satellite itself). The solar arrays are always pointed to within 25 degrees of the sun; if the pointing error was as much as 3 degrees, the worst case loss in energy collecting efficiency would only be 2.6% relative to the 25-degree-angle case. In other words, no big deal from a power-generating standpoint. When the solar arrays are supposed to be pointed 10 degrees away from the sun, they could be off-pointed by 6 degrees with a power loss of only 2.4%. However, that same 3-degree (or greater) error can have a huge impact on the predicted flare brightness, and can also shift the flare time by 15 seconds or more depending on how low in the sky the flare is expected to occur. The bottom line is, don't expect too much accuracy from IRIDFLAR's solar array flare predictions -- treat them as extra opportunities to see Iridium satellites at brightnesses far greater than their typical appearance from purely diffuse solar reflectance. Cheers, Rob ----------------------------------------------------------------- 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
This archive was generated by hypermail 2b29 : Tue Jun 12 2001 - 13:45:02 PDT