Hi Kevin, > Arles,France,43633N, 4.717E > Yes Bruno the Top Solar Panels Casted a shadow at 17:59:04 > on the Zarya,And the Zvenda Modules.The mag of the ISS was > then reduced to a magnitude 6.2 From this Shadow.The > Shadow lasted 3-4 seconds it looks like on This screen. Respectfully, this is a mistake. There is absolutely no sunlit configuration of ISS that will drop its magnitude by a factor of over 200 from its peak (but non-specular) brightness -- assuming you're not talking about trying to observe ISS at an elevation of 3 degrees above the horizon. This is not a stealth space station, and the solar panels are not 99.5% absorptive. I appreciate that you've done a lot of work to model the 3-D structure of satellites, but without continuous, precise pitch, yaw and roll orientation as a function of time, and the optical properties of all major external surfaces -- not just reflectivity, but bireflection distribution functions -- you cannot predict the visual magnitude of a complex object like ISS to any better than about a factor of 2 (.75 visual magnitudes). As for spinning or tumbling satellites, except for the special circumstances of spin-stabilized nadir-pointing satellites, or satellites for which spin axes have been derived from multiple observations, you cannot accurately predict when they will glint. You can forget the tumbling Iridium satellites -- they have far too many specular surfaces (I know of at least 10 major ones, some of which can be involved in double or even triple bounce reflections) to deconvolve their tumble dynamics. Only through a tremendous amount of observational effort (years of data from dozens of observers) have the spin dynamics of Superbird A (#20040) been determined. To a lesser extent, the axes of TDF-1 (#19621) and ETS-6 (#23230) have also been derived, though not their long term precessions. I want to reiterate that I applaud your efforts in working to uncover the rotational dynamics of specific satellites with the goal of providing glint predictions for our list members. I share your goal, as do several others on our list, and have been doing just that for many years, within the limits of what can be divined with eyes, binoculars, telescopes and stopwatches. Enthusiasm is ALWAYS welcome here! I would only caution that your enthusiasm be tempered by an equal amount of skepticism until your model's predictive accuracy has been confirmed by multiple observations. Overstating the model's predictive powers before it has been "put through its paces" only does a disservice to the people who sit out in the cold at 2 am to record the observations that make all this magic possible. Best wishes, Rob Matson ----------------------------------------------------------------- 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 : Thu Dec 14 2000 - 10:31:50 PST