GMOS-S upcoming intervention

July 18th, 2023

GMOS-S will be removed from the telescope on Friday, July 21st for the CCDs intervention, with the purpose of replacing the faulty CCD2.
The instrument is scheduled to come back during late August for the commissioning of the upgraded detector array, and expected to be available for Science by September.

GMOS-N B600 PIs are encouraged to use B480 grating

June 16th, 2023

The GMOS-N B600 grating sensitivity has recently degraded significantly. This overall degradation is in addition to the blue sensitivity loss reported previously. Since the new B480 grating is now available for GMOS-N, we recommend changing B600 programs to the B480 grating. The B480 grating offers a wider wavelength coverage than B600 at a a slightly reduced spectral resolution.

On GMOS-S MOS data reduction: fixing MDFs

November 29th, 2022

After the GMOS-S detector troubleshooting earlier this semester, the physical location of the array has shifted by a small amount in the -direction. While this did not have harmful consequences, the Y-shift has the effect of the MOS mask slits as defined on the MDF appearing with a small (~20 pix) yet systematic offset with respect to the actual location of the spectra.

Reduced blue sensitivity of GMOS-N B600 grating

September 9th, 2022

It has recently been noticed that the sensitivity of GMOS-N B600 observations at wavelengths blueward of 500 nm is significantly lower than predicted by the Exposure Time Calculator. Historic data of spectrophotometric standard stars show that this reduction in sensitivity is largely attributed to a decrease of the B600 grating response, which started to develop around 2013 to 2014. 

GMOS-S CCD2 issues

August 12th, 2022

The repair attempted during July was not successful, and the problem on CCD2 (amplifier #5) persists. On the other hand, the noise patterns on CCD2 and CCD3 are gone.

The situation will remain like this during semester 22B since the only possible solution requires a major intervention, which is not planned for the current semester.

Webpage on GMOS-N detector status

March 18th, 2022

A new webpage with information on the current status of the GMOS-N detector array is now available here. The webpage provides details on the recent hot column features (see March 10 announcement) and updated recommendations for dither strategies to minimize the impact of the hot columns on science data. Any future updates from the ongoing characterization of the hot columns will be posted on this webpage.