Asteroid photometry is nothing but the study of fraction of solar radiation, which is reflected by the surface of small body. Here we examined the photometry of Apophis, a big/elongate metal rich asteroid passing by near to earth.
If we assume that asteroid Apophis is metal rich, it could reflect good part of solar radiation at V band as well as R Band. The tendency of photon reflection decrease from V (short wavelengths) to R (longer wavelengths) band. Here we took the assumption that sun is G2V type star, so most of photons are towards yellow + red end and hence small body is reflecting more photons at R band. These are just assumption to make task interesting. Anyway!
The second point is that if asteroid is perfect spherical body, spinning around random axis will reflect same flux towards telescope, but case will be different if small body have irregular structure. In this case the flux reflected will be proportional to the cosine of area seen by telescope and depend on angle between sun/asteroid/earth.
In our study, we dragged the R band flux w.r.t time. The FITS generated and examined using PriSMv10 batch photometry using UCAC4 catalog. The results are shown below.
We should not forget that Apophis photometric curve was measured w.r.t standard stars and as soon as sun and asteroid changes the position in sky, the incident solar flux does not remain constant. It can be seen that the magnitude at the end of observation goes too high.
Bessell (B): +*.*, Bessell (V): +*.*
Bessell (R): +15.2, Bessell (I): +*.*
TELESCOPE: C11, 1623.0mm
ORIGIN: Cepheid Observatory, India, Vorion Scientific, India
V.K.Agnihotri, B. Kumar, S. Mahawar, K.Vora