AMBER Overview


AMBER is a near-infrared interferometric instrument, combining simultaneously the light coming from three telescopes. AMBER is offered with various VLT-I configurations that employ either the Unit Telescopes (UTs) or the Auxiliary telescopes (ATs) as its stations. All possible triplets of UTs and three specific AT quadruplets are available. For the precise telescope positions and baseline lengths of the different AT and UT baselines, please see the VLTI Configuration page. AMBER is also offered in conjunction with the FINITO fringe-tracker which allows longer detector integration times and hence can reach fainter magnitudes.

Because of the limited time available for VLT-I in UT mode compared to AT mode, it is recommended that a scientific program that wishes to use the UTs is designed such that scientifically meaningful results can already be achieved in a single night.

Spectral modes and coverage

AMBER offers the following spectral settings: low resolution (35) covering both H and K band (LR-HK), medium resolution (1500) in K band (MR-K), medium resolution in H band (MR-H), and high resolution (12000) in K band (HR-K). For central wavelengths and wavelength coverages for these four spectral settings see the AMBER Instrument Description. There is the usual trade off between the spectral range that can be recorded and the choice of DIT.  

Integration times

AMBER programs that make use of FINITO allow DITs on AMBER exceeding substantially the local coherence time without compromising significantly the fringe contrast. It also allows the readout of the full chosen spectral band. FINITO is used by default in MR and HR. When the fringe tracker FINITO cannot be used (e.g. for faint and/or extended objects or sources at high airmass), the DIT has to be short in order to minimise the detrimental influence of the atmospheric turbulence on the fringe contrast. For LR-HK and MR-K without FINITO on the UTs the DIT is fixed to 25 milliseconds, while on the ATs the DIT can be 25, 50 or 100ms  when absolute visibility measurements are the goal. For measurements of the closure-phase and differential quantities without FINITO, the maximum allowed DIT is twice the DIT allowed for absolute quantities. If DITs longer than this are wished then this can only be performed in Visitor Mode (under exceptional weather conditions).

During phase II preparation after acceptance of a program, a waiver should be submitted for programs without FINITO in MR and HR settings.

Please refer to the instrument description page for limiting magnitudes.

Execution times

The execution times in AMBER are fixed for cal-sci and cal-sci-cal sequences. Please refere to the AMBER User Manual for more information.

Further Information

All information about AMBER can be found in the user manual


For questions and inquiries on AMBER observations, please contact the Paranal instrument scientist (see Instrument Operation Team page).