GHOST has returned to service following the successful replacement of the ThAr arc lamp in GCAL. Arc counts have returned to normal, and the instrument will be offered again starting tonight (2025-03-26 UT).
Important information for PIs:
A degradation in the arc lamp was identified beginning around 2025-02-13 UT, which affected the wavelength calibration of data taken during that period.
GHOST is currently unavailable due to the replacement of the ThAr arc lamp. Troubleshooting began on Tuesday, Mar 25, and is still ongoing.
A sudden drop in arc lamp intensity was identified starting on Feb 13, which has continued to decline over time. This degradation has affected the wavelength calibration, introducing uncertainties in the data.
PIs of GHOST programs taken between Feb 13 and now are advised to use arc images acquired before Feb 13 for wavelength calibration.
Seven lens interfaces in the GMOS-N collimator were refilled with index-matching oil on 5 March 2025 HST. This work was performed to address the known recurring issue of air bubbles developing in the GMOS lens interfaces.
The air bubbles move with changes in telescope elevation and cass rotator angle and can cause a shifting partial obscuration in the lower part of the GMOS frames. This results in a limited flat fielding accuracy, particularly impacting imaging data that use the entire GMOS field of view.
We are pleased to announce that a video tutorial for setting up GHOST Phase II is now available online. Check it out here: https://noirlab.edu/science/videos/ghost
We hope you find it helpful!
MAROON-X experienced two shifts in the echelle image in 24A: the first due to an earthquake on Feb 9, 2024, and the second due to a loss of observatory power on June 13, 2024. This has impacted two key steps in the reduction process. As a result, the radial velocities from 24A based on the existing reduction are currently uncertain to ~20 m/s. All data from 24B so far seem to be within specifications. The instrument team in Chicago has been adjusting the reduction procedure with the aim of resolving this issue and restoring the nominal data quality.
The issue affecting every 8th column on the top right quadrant of the detector reported in this announcement has been further investigated.
The two ADC boards that were not performing correctly have been replaced and the issue has now been fixed. The figure below shows a horizontal cut along the top right quadrant of a LR-IFU flat and demonstrates that the faulty columns are now recovered.
Flexure effects within GMOS can result in wavelength zeropoint shifts if the on-sky science data are wavelength-calibrated using daytime CuAr arc exposures.
In early April 2024, the GNIRS camera turret experienced a mechanical issue, likely due to the dragging of a bearing that helps drive the movement of the turret. It has been assessed that GNIRS could no longer reliably shift between its long and short cameras. A soft lock on the camera turret has been put in place, which fixes the location of the turret to the short blue camera.
As part of the Gemini Instrument Upgrade Program GNIRS has gained two new optical sub-systems, namely the LR-IFU and the HR-IFU. The commissioning of both IFUs has now been completed.
GNIRS recently began showing an issue that affects every 8th column on the top right quadrant of the detector, an issue that impacts all GNIRS modes. This issue first appeared on the 25th of October, 2022. Investigations to mitigate or fix the issue are currently ongoing. For the time being, PIs are advised to consider all pixels associated with these columns as bad pixels and not to use them for science and/or calibrations.