Asteroids as calibration standards for Gaia's RVS

In addition to two astrometric telecopes Gaia will carry a Radial Velocity Spectrometer (RVS). This will be a self-calibrated instrument using spectra obtained during the mission to calibrate the wavelength scale of the instrument. To ensure reliable and consistent calibration a large number of objects with accurately known radial velocities are desirable.

Tomaz Zwitter (University of Ljubljana) and Françoise Crifo (Observatoire de Paris-Meudon) reviewed the suitability of existing radial-velocity standard stars as wavelength calibration standards for the RVS. They concluded, taking into account the saturation limit of the instrument, that few of these stars would be accessible to Gaia. To supplement the stars that remain they propose including RVS observations of suitable asteroids whose radial-velocities are well-known. The distribution of asteroids is such that the RVS will typically observe 1 standard star and 2 bright asteroids in each 6-hour revolution.

The image above shows asteroids (and comets) brighter than V=15 on 19 September 2003 at 13h GMT, plotted in ecliptic coordinates centred in the anti-Sun direction. Coloured lines indicate the area covered in one 6-hour rotation of Gaia around its axis. Red: when the satellite axis lies in the ecliptic plane. Green: when the satellite is at the greatest elongation from the ecliptic.

The report Asteroids as wavelength calibration standards for the radial velocity spectgrograph of the Gaia mission prepared by Tomaz Zwitter & Françoise Crifo is available from the RVS consortium web site

Image courtesy of Tomaz Zwitter & Françoise Crifo.

[Published: 03/11/2003 ]