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. 

• PIs of GHOST program observed between 2025-02-14 UT and 2025-03-25 UT are advised to use arc frames acquired before February 13 or after March 26 for wavelngth calibration. 
• The US-NGO reduced data currently available in GOA for this period may contain wavelength calibration uncertainties. These datasets will be replaced re-reduced versions using pre-Feb 13 arc frames. This process is expected to take a few weeks. 

If you have any questions, please contact your contact scientist or the GHOST science team ghost_science@noirlab.edu