Arte Journal, Saturday, May 17, 2025.

Our teams have made significant advances in commissioning of the DDRAGO instrument on the COLIBRÍ telescope. Although much remains to be done and there are important limitations, the telescope and instrument are already producing science-quality data.

Our medium-term plan is to have the telescope and instrument fully commissioned and operational before the start of the 2025B semester and to offer time to the Mexican and French communities through their respective Time Allocation Committees.

However, as we move towards this goal, and in consultation with INSU/CNRS and the Director of the Instituto de Astronomía, we have decided to offer early science time to our communities in a limited, shared-risk manner.

Some important points to consider are:

• The instrument and telescope are not yet fully commissioned. This means that certain components are either not working, not yet integrated, not tuned, not characterized, not documented, and not fully understood. These limitations are presented in more detail below. We expect to resolve all of these limitations before the 2024B semester.
• The main focus of the engineering teams will be to continue to work to commission and document the instrument, telescope, pipeline, scheduler, and other components.
• Nevertheless, we aim to schedule 1 hour per night for projects from the Mexican community and 1 hour per night for projects from the French community. We will attempt this on a best-effort and shared-risk basis, on the understanding that commissioning tasks and the transient science program may take priority, and with the warning that the instrument is not yet fully characterized.
• The available time is very limited. As we progress with commissioning, we may be able to increase the time available.
• We request that proposers have patience with us as we work out appropriate procedures.

How To Request Early Science Time

Proposers should prepare a 1-page request in PDF:

• Each request should have a title and a date.
• Half of the page should be a scientific description, largely so that the science operations team can understand the science aims of the observations and thereby program them out in an appropriate manner.
• The other half should be a technical description, including target coordinates, exposure and filter sequences, and cadences for repeats.
• If need be, additional pages can include figures.

While both individuals and groups may send requests, each request should clearly indicate a single technical contact person and give their email address; all correspondence will be with this person.

French proposers should send their requests to the COLIBRÍ PI (Dr. Stéphane Basa, stephane.basa_AT_lam.fr).

These persons will forward the proposal to the science operations team. This team may communicate with the technical contact prior to the observations with advice or to seek clarifications. The team will also communicate with the technical contact when the data are available. If there is oversubscription, the science operations team will seek guidance from these persons.

In agreement with the MoU governing COLIBRÍ, the science operations team will treat the requests and data with professional confidentiality. They may examine the data to verify its quality and to characterize the instrument. They will not share the data outside of the science operations and instrument teams.

There is no requirement to include members of the science operations team as authors on any publication that results from these observations. However, we request that any publication cite the telescope and instrument papers and acknowledge the use of DDRAGO and COLIBRÍ; details are in the observing manual linked below.

Observations

The DDRAGO instrument is currently operating as a single-channel imager with a field of 26 arcmin, pixels of 0.38 arcsec, and g, r, i, gri, and B filters.

The transients team currently observes by taking 60 seconds exposures and dithering randomly in a circle of diameter 1 arcmin. This seems to give a good balance between efficiency, reaching the sky limit, being able to form a sky image, and not losing too much image quality to telescope tracking errors. Other strategies are possible, and one of the aims of this shared-risk time is to allow observers to determine the best strategies for their science and to communicate their requirements and experience to us.

We aim to keep individual observing blocks to about 30 minutes of real time (i.e., 24 x 60 second exposures plus overheads). If more data is required, we recommend repeating blocks.

A simple exposure time estimator is here.

A preliminary observing manual is here.

This manual will be updated as the instrument is commissioned.

Current State Of the Instrument and Telescope (25/02/2025)

The current state of the instrument is as follows:

• The blue (g/r/i/gri/B) channel is operational and works as expected.
• The red (z/y/zy) channel is not operational. The CCD compressor was damaged during shipping and will need to be repaired by the vendor. It is quite possible that the red channel will not be available before June 2025.
• We have not yet completed optical alignment of the telescope or the blue CCD. Nevertheless, the instrument has given images with FWHM of 0.8 arcsec in the center of the field. The blue detector seems to be slightly tilted with respect to the focal plane, and the FWHM in our best images degrades to about 1.6 arcsec in the upper-left and lower-right corners of the full 26 arcmin field. We have tentative plans to perform fine alignment of the CCD in March 2025.
• There is vignetting in the outer two arcmin of two corners of the field as the CCD is not yet centered on the optics. We have tentative plans to center the CCD in March 2025.
• The automatic data-processing pipeline is still in tuning phase.
• The scheduler is not yet fully integrated. Observations have to be programmed by hand, which limits flexibility and favors blocks that are simpler to program.