The three objectives listed above have been addressed in parallel since the beginning of the project, and this has lead to the publication of several scientific articles, and the organization of a workshop.
2 PhD, 1 postdoc, and one engineer have been hired to work on the project. I am explicitly referring to them in this summary.
1 - Exhaustive work has been performed to push the performance of ELT/HARMONI.
1.1 - an optical experiment has been improved and used to reproduce in the laboratory the capability of HARMONI to measure and correct the small, quasi-static optical aberrations that could ultimately limit its performance. It was in particular used to demonstrate the ability to keep the residual error small enough in spite of residual atmospheric dispersion, and atmospheric turbulence. PhD student A. Hours has worked on this part of the project, in collaboration with colleagues at LAM, and in other institutes that are part of the HARMONI consortium.
1.2 - FastCurves, a semi-analytical noise propagation model has been developed by PhD student A. Bidot to estimate the limitation to the spectral analysis of the star and planet signals that will be obtained with HARMONI. This work now enables to estimate the capability of HARMONI to detect and characterize planets in various cases of star magnitude, planet differential magnitude, type, and separation, integration time, etc, and for the various observation modes of HARMONI. All of this could not be done with the classical end-to-end approach, and this type of model can be adapted to many other instruments. Early results indicate that HARMONI could study planets up to 10 times fainter than the ones that have already been observed. The FastCurves package is available online, and it has been actively shared with the community.
1.3 - a second optical experiment has been designed, and partially installed to reproduce in the laboratory the images that ELT/HARMONI will provide, so as to test the data processing algorithms that will later be used on the real data. The installation wad not completed at the end of the period covered by this report, and no results is therefore reported here, apart that no showstoppers have been encountered.
2 - Robust, adaptative amplitude control of a light beam has been tested in the context of the preparation of ELT 2nd generation instrument.
2.1 - a third optical experiment has been designed, installed, and used to successfully test the capability of a commercial micro-mirror array to spatially mask out part of a telescope beam, together with a wavefront control system. This work was performed by PostDoc L. Leboulleux (now a permanent staff at IPAG). This involved the development of a control procedure, which was done by software engineer S. Curaba. The results of this experiment indicate that this device - which was not designed for this application - can indeed be used to adaptively mask the pupil to change the point-spread function of the telescope to enable the observation of planets next to the star. The main limitation that was anticipated is its too high chromaticity, and this was confirmed in our results.
2.2 - PostDoc L. Leboulleux has developed a novel way to design components robust to two different types of severe optical aberrations: co-phasing errors of segmented telescopes, and differential piston errors encountered in low-wind conditions. Her results indicate that these aberrations, while their amplitude should be kept as low as possible, can some extent be countered by her design. Without it, instruments designed to characterize planets can see their performance severely limited.
2.3 - we have identify an alternative type of micro-mirror array, which was recently developed at the Fraunhofer Institute in Dresden, which should be capable of achromatic amplitude control (and possibly phase control as well). More work will be necessary to confirm this.
3 - A first demonstration of a high transmissive, compact, high-resolution spectrometer has been performed, as a first step towards its potential use as a visitor instrument.
3.1 - The VIPA spectrometer developed at IPAG has been calibrated and demonstrated at the Palomar Observatory using the 5m Hale telescope in March and April 2022. This was a collective effort of my team, and specifically involved the work of PhD A. Bidot, and software engineer S. Curaba. This demonstration was delayed about for about 1.5y because of the COVID-19 pandemic, which shut down observatories worldwide for months, and limited their access for an additional year. The test confirmed the data obtained in the lab (spectral resolution, transmission). Moreover, it was especially useful to check that the operation of the spectrometer was quite easy. Its optical interface with the rest of the observatory consists in two optical fibers, which simply need to be connected to the spectrometer. Apart from a few hurdles due to the observatory itself, the optical fine alignment, and the overall setup of the spectrometer took about 10days. Observations were performed over 3 nights, including some hours during which data was obtained with both the VIPA spectrometer, and PARVI, a local spectrometer observing at the same wavelengths.
3.2 - The first demonstration used an engineering grade detector provided on a temporary basis by U. de Montréal. A new scientific grade detector has since been purchased by the project, and modifications have been made to the mechanical structure, and the electronics of the spectrometer to enable its installation. Fibered gas cells have been purchased, and tested in the laboratory. They will be used to perform a fine wavelength calibration in the 2-2.5um spectral range (calibration in the 1.5-1.7um range is performed thanks to a tunable laser also purchased by the project).
This work has lead to several peer-reviewed publications, some of which pertaining to the period covered by this report) are currently under review. This work has also been presented in several international conferences (Spirit of Lyot, SPIE, AO4ELT-7) for which conference proceedings have been written.
