Thermal Infrared MultiMode Instrument
TIMMI (Thermal Infrared MultiMode Instrument) was a combined camera and spectrometer installed on the ESO 3.6-metre telescope at La Silla. It was based on the detector of ISOCAM, flown on the ESA Infrared Space Observatory (ISO). TIMMI registered light in the mid-infrared part of the electromagnetic spectrum, ranging from 5–17.5 µm, which is valuable for studying the birth of stars and the formation of circumstellar disks and planets. In order to reach sufficient sensitivity at infrared wavelengths, liquid helium had to be used to cool TIMMI’s camera to approximately -260°C, just a few degrees above absolute zero.
Ground-based observations at wavelengths greater than 5 µm are dominated by the strong sky background: even seemingly empty sky is still fairly bright due to diffuse light in the Earth’s atmosphere. This makes it difficult to detect the fainter light of a target object. At mid-infrared wavelengths, this background radiation changes very quickly on time scales faster than a second. Ground observations therefore require a specific observing technique. For TIMMI this involved a “chopping” secondary mirror, which constantly underwent cyclic movements (“wobbled”) with an amplitude of a few millimetres, changing between the object of interest and the nearby sky. The two images were then subtracted, leaving only the light from the object.
TIMMI was extremely productive. Among its many discoveries, TIMMI showed the presence of a disk around a hot and massive star for the first time (eso9828), observed the impact of Comet Shoemaker-Levy 9 on Jupiter (eso9402), and studied the dramatic brightening of the Periodic Comet Schwassmann-Wachmann 3 (eso9601).
TIMMI was in constant use from 1992 to 1998, when it was decommissioned because the development of detectors had progressed so rapidly. In fact, in 1993, ESO had already joined a consortium of French institutes to develop a next-generation device based on the array used in TIMMI, and thus TIMMI was replaced by TIMMI2 in 2000.
TIMMI2 was built by the Friedrich-Schiller-Universität (FSU) in Jena, Germany. It was interfaced to the ESO 3.6-metre telescope with a special infrared adaptor and detected infrared radiation in the mid-infrared spectral region, from 5–24 µm. At the time of its first light, it was the most sensitive and versatile instrument of its kind available in the world and put European astronomy at the forefront of research in this field.
TIMMI2 was particularly well-suited for observations of the complex processes that take place in the innermost regions of star-forming clouds. Among the first images taken by TIMMI2 were some of the most penetrating mid-infrared views ever obtained of the central region of the Orion Nebula (eso0113).
Seeing the Universe in the mid-infrared region opened TIMMI2’s eyes to study a variety of astronomical objects including active galactic nuclei, starburst galaxies, comets, other planets, variable stars, and compact objects like galactic centres, in addition to protoplanetary disks around young stars and brown dwarfs.
TIMMI2 was discontinued in 2006.
This table lists the global capabilities of the instrument. The authoritative technical specifications as offered for astronomical observations are available from the Science Operations page.