GMOS

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 noise problem on CCD2  persists. 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. 

GMOS-N status update

March 10th, 2022

The GMOS-N detector issue reported on March 2 has largely been resolved by the full thermal cycle performed between March 2 and 3. The extended bright columns on amplifiers 7 and 12 are no longer present. The narrow bad column of hot pixels on amplifier 5 persists and saturates in longer science exposures. The following figure shows the hot column in an overscan-subtracted bias image (as marked by the blue arrow). 

Bias image showing the new hot column

New GMOS-N bias features

March 2nd, 2022

The GMOS-N detector has shown new bias features since an uncontrolled warm-up of the detector on February 26, 2022 . These features consist of a narrow bright column on amplifier 5, and broader bright columns on amplifiers 7 and 12. As a first measure to address this new issue, a full thermal cycle of the detector is being performed starting from today. GMOS will be unavailable for the next couple of nights until the thermal cycle is complete.

GMOS-S is back!

October 8th, 2021

After a thermal cycle performed over the weekend, the detector amplifier #5 is back to its normal perfromance. CCD1 CTE is also nominal, and OIWFS performance is OK after the succesful repair that had been performed during September. Therefore GMOS-S is back at full capacity.

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