Effects of Fabry-Perot Etalon Fringes on Asteroid Reflectance

Our research aims to build a high-speed data analysis pipeline (DAP) to process filtered photometry asteroid observations. Rapidly generating reflectance plots via DAP minimizes the work hours required and decreases the latency from observations to science for newly discovered NEAs and the expansion of SDSS’s Moving Object Catalog results.

Our primary data collection telescope has been the SMARTS 1.0m telescope at CTIO using Sloan griz filters. As we tested the DAP, we discovered a series of unexpected results. First, our results showed instability in the i and z filters; we initially thought this was evidence of taxonomically ambiguous asteroids. However, the instability occurred within minutes, which would be much too fast for the rotation of a main-belt asteroid. Instead, we discovered that Fabry-Perot Etalon fringes are not being removed using the standard Flat/Dark/Bias calibration model. Since the fringes only occur beyond 700nm, they affect the i and z filters.

Second, we discovered that source extractor produces erroneous photometry near the etalon fringes. Therefore, as an asteroid would move over a fringe, the erroneous photometry would cause instability in i and z.

At AAS-240, we will present our current results on building the DAP and the multiple issues overcome to obtain photometry when data suffers from etalon fringes.