ISAAC observes Jupiter occultation

A few days after the "First Light" of the VLT Infrared Spectrometer And Array Camera (ISAAC) at the first 8.2-m VLT Unit Telescope (UT1), cf. ESO Press Release eso9856, the ESO Team of astronomers and engineers at Paranal have succeeded in observing a lunar occultation of Jupiter with the new instrument. During this event, that took place on 28 November 1998, the dark rim of the Moon's disk moved in front of the planet, covering it from view. Somewhat later, Jupiter reappeared behind the opposite, illuminated rim.

The ISAAC Team made use of this occasion to perform further test observations with ISAAC and the 8.2-m VLT UT1. For this, short exposures were made at the ISAAC Long Wavelength arm through a narrow band (1.5%) filter centred at wavelength 3.2 µm. They lasted 4 sec during the early phase of the occultation and decreased to 0.8 sec, then 0.4 and finally 0.08 sec, as progressively brighter areas of the illuminated part of the Moon's surface moved into the field-of-view.

This first, short sequence shows the first phase of the occultation (ingress) during which the dark Moon rim (upper left) covers Jupiter's disk. The bands in the planet atmosphere are well visible, and the polar areas are bright at this infrared wavelength. In this and the following video, the Moon moves from left to right, corresponding to West-to-East in the sky.