FRIDA will be, so far, a unique ground-based instrument comparable to space telescopes, as it will have better sensitivity and spatial resolution than similar instruments attached to other telescopes. This is because it will work in conjunction with the Gran Telescopio de Canarias (GTC), with a collecting area of 10.4 m, and making use of the (GTCAO) adaptive optics system, which will be able to correct, in real time, the distortions produced by the turbulence of the atmosphere.

It is designed to operate at the diffraction limit in the 0.9 μm a 2.5 μm wavelength range to capture the relatively cool, near-infrared light emitted by the Universe.

It will have two separate modes of operation, imaging and integral field spectroscopy, using a single HAWAII-2RG™, such that the user will be able to switch between them and perform a selection of the field of interest facilitating an acquisition in the small of the Field of View (FoV) integral field unit (IFU). In addition, it will have 3 different resolution scales:

40 arc-miliseconds/pixel (coarse scales)

20 arc-miliseconds/pixel (medium scale)

10 arc-miliseconds/pixel (fine scale)

It should be noted that currently no other instrument in operation on large telescopes has a scale similar to the fine (for reference, the Hubble Space Telescope, HST, operates with spatial scales on the order of 50 and 100 arc-miliseconds/pixel).

The FRIDA design also contemplates the use of Lyot masks, as well as classical and apodizing Lyot apertures. The use of these devices will allow the image of a bright object to be masked and the image or 2D spectrum of its surroundings to be obtained.

A key advantage of FRIDA over similar instruments is that it does not rotate and it is the GTCAO system that provides the rotated field, thus ensuring its stability with minimal bending and a precisely calibrated distortion pattern

Image mode

When the imaging mode is selected, the corrected beam coming from the adaptive optics system passes through the collimator-camera system before being diverted to the detector. In this path, before reaching the detector, it is possible to choose different broadband or narrowband filters in addition to one of the three different scales available.

The 10 arc milliseconds per pixel scale (fine scale) allows an adequate sampling of the first Airy ring, limited by diffraction in the Z and J bands.


The 20 arc milliseconds per pixel scale (medium scale) allows adequate sampling in the H and K bands, where the adaptive optics system is expected to reach its maximum correction.

The 40 arc milliseconds per pixel scale (coarse scale) was designed primarily for acquisition purposes in IFS mode.

The following image shows an example of how the images will be enhanced after passing through GTCAO and will be acquired by FRIDA using the mean scale.

Field integral spectroscopy mode

FRIDA's field integral spectroscopy mode allows to do what is called 2D spectroscopy using a monolithic field integral unit, with various powers of spectral resolution:

R = 1 300 (low) to cover H+K (and also Z+H)

R = 4 000 (intermediate) on Z, J, H or K

R = 30 000 (high) in selectable windows in a range of 1.4 μm a 2.4 μm

The high resolution is unique among similar telescope instruments in the class of 8-10 m collecting area.
The FRIDA slicer makes 30 slices with 66 pixels/slice in the spatial direction and 2 pixels per resolution element in the spectral direction, so it will be able to segment the images into thirty sections while preserving both the spatial and spectral information of each section, so combining high spectral resolution with high spatial resolution makes it a unique instrument in its class.

In this mode, the instrument acquires a configuration in which the optical beam, after passing through the scale-defining chamber, will continue to the integral field unit (IFU) and the double-pass spectrograph to the desired diffraction grating and finally to the detector.

A schematic of how this mode operates is shown below: