VIRTIS / Rosetta

First light of Virtis-H

Wednesday 7 July 2010, by St├ęphane Erard

These data were obtained during VIRTIS-H ground tests in Meudon in 2001

A pre-calibration of the VIRTIS-H channel (FM) has taken place in Paris/Meudon Observatory in April 2001. As a conclusion of this pre-calibration, samples of different minerals have been observed in reflectance by VIRTIS-H. A lamp was used with a filament temperature of 2000 K, and the sample (powder, placed in a cupper cell) was illuminated at 40┬░ incidence.

VIRTI-H mineral spectra
VIRTI-H mineral spectra

VIRTIS-H ground tests in Meudon

Figure 1 shows the spectra for the following mineral samples:
Montmorillonite (3), Enstatite (2), Augite (1), Hawaiian green sand (4), Coal (1), Juvinas meteorite (3), Quirico mixture (PAH/alanine/POM) (1)
Source of materials: (1) Institut d’Astrophysique, Orsay (2) Osservatorio Astronomico di Capodimonte, Napoli (3) Museum d’Histoire Naturelle (4) Personal collection

VIRTIS-H ice spectra
VIRTIS-H ice spectra

VIRTIS-H ground tests in Meudon

Figure 2 shows the growth of ice crystals over a cold plate, initially at the liquid N2 temperature, observed as ice deposits grow over the plate through time. The increase of reflectance at 2 micron is due to the ice reflectance covering the dark plate. Simultaneously, the ice band becomes broader and broader at 3 micron.

VIRTIS-H was still in a preliminary state, before complete calibration occurred in Orsay. The absolute reflectance is uncertain, due also to approximate background subtraction. These spectra were shown for illustration and VIRTIS-H testing of capabilities, and should not be used for a higher level scientific purpose.