A.V. Mironov, G.N.Kolesnichenko, A.V. Martyshin, S.V. Logunov
The transformation of light signal to electric charge for photometric measurements by the use of carge-coupled device (CCD) is examined. All processes are considered for heterochromatic case. The definition of the limiting magnitude of an optical-electronic system (LMOES) is gaven on the base of a signal-to-noise ratio. An algorithm for correcting calculation of the LMOES is described for two cases: observations from Earth and from a satellite in a circumterrestrial orbite. For calculating, the following function was took into account: energy distribution in a space object spectrum, spectral response of a detector, spectral Earth atmospheric transparence. The sources of the initial data necessary for the calculations are presented.
The execution of the algorithm is illustrated by two examples: 1) calculation of the maximum distance, where a space object illuminated by Sun can be found, and 2) calculation of the colour characteristics (colour indices U – B, B – V and V – R) for two spacecrafts with two types of outer cover. The results are a fact that for adopted parameters the spacecraft covering by steel can be found in the distance of 200 thousand kilometers with the probability of 99.7% The extra-atmospheric star magnitude of such object is equal 13.4 mag and is the maximum for the adopted parameters. Measurements of the space object star magnitude with relative mean-square error less than 10% are possible for distances no more than 100 thousand kilometers. If the spacecraft is covered with vacuum-screen heat insulation “Mylar” then maximum distance for finding the object decrease two times and the limiting magnitude became 11.9 mag as Mylar has ability for light reflection lesser than steel.
Moving the measuring apparatus from space to terrestrial high altitude observatory decrease the maximum distance for object finding more than two times in comparison with extra-atmospheric case.
Calculating the space object colour indices for different outer cover shows that the method has good prospects to recognize types of the objects The fulfilled model calculation show that space object with different cover has colour indices which significantly differ from each other.