GeminiFocus April 2019 - Page 19

The members are: Abhijit Saha (US; NOAO) - Chair; Andres Jordan (CL); David Sand (US); Basilio Santiago (BR); Meg Schwamb (Gemi- ni); Federica Bianco (US); Myungshin Im (KR); Maria Drout (CA); Craig Heinke (CA); Victoria Alonso (AR); Alexander Vanderhorst (US); Andy Adamson (Gemini, in attendance); Bryan Miller (Gemini, in attendance); John Blakeslee (Gemini, in attendance). Not all of the members of this time-domain advisory group work on time-domain sci- ence; the mission of the group includes protecting the completion of non-TDA pro- grams in the coming Large Synoptic Survey Telescope era when we expect to have an increased number of Target of Opportunity proposals. We are grateful to Abi and the group for helpful commentary to date. TOPTICA Laser: Available Every Night! With a fully commissioned TOPTICA laser, we are back in operation for Laser Guide Star (LGS) mode at Gemini North. The 19A semester will be a “transition” period from scheduled laser blocks to a fully-integrated LGS queue operations model. This will al- low for LGS programs to be observed on any night when conditions allow, giving Gemini Principal Investigators access to LGS adap- tive optics observing throughout the semes- ter (Figure 1). The Next Generation Natural Guide Star Sensor for GeMS Gemini-South’s Multi-conjugate adaptive optics System provides for an adaptive op- tics (AO) corrected field of about one arc- minute. To achieve this important capabil- ity, the system relies on a constellation of five laser guide stars and up to three natural guide stars in order to sense and correct for atmospheric turbulence. The original design of the natural guide star sensor has been in operation now for several years. It is based around three mechanical probes picking up stars in the field. Each probe channels the light onto optical fibers leading to avalanche photodiodes for fast centroiding. Unfortu- nately, the sensitivity of this system leaves much to be desired, and the mechanical ar- rangement is complex in operation. Therefore, some years ago, Gemini entered into a collaboration with the Australian Na- tional University (ANU) to develop a better system designed around the now available high-speed Electron Multiplying (EM) CCD cameras. Using an EM CCD imager will re- sult in much improved sensitivity. The mov- ing probes will no longer be necessary, as the full patrol field will be imaged onto the CCD, while regions of interest around the se- lected stars will be read out at high speed to provide centroiding information to the Figure 1. Gemini Science Operations Specialist Michael Hoenig (back) and Gemini Senior Laser Technician Jeff Donahue discussing LGS operations for the TOPTICA laser in the Gemini Base Facility Control Room in Hilo. Credit: Jeff Donahue April 2019 GeminiFocus 17