GeminiFocus April 2018 | Page 20

2017B Retrospective Now that we’re in 2018A, the time has come for a brief recap of events in 2017B at the two Gemini sites. Mixed fortunes with the weather, plenty of visiting observing, and some exciting astronomical events charac- terized the semester. Hawai‘i At Gemini North, the semester started later than usual while we finished repairing the shutter in late August. That, combined with weather loss later in the semester, meant that we had less science time on-sky than usual. This adversely hit completion rates in Band 1, but Band 2 programs held up reason- ably well compared to previous B semesters. When we were on the sky, conditions were reasonably good and so Band 3 completion rates ended up relatively low. Visiting observers came through Gemini North fairly regularly, conducting four short classical runs and three more extended Pri- ority Visitor runs. Figure 1. The number of nights on which Gemini South responded to a Standard ToO request (left) and a Rapid ToO request (right). 18 Following up on the interstellar asteroid ‘Oumuamua (see the January 2018 issue of GeminiFocus, page 4) kept us busy and ex- cited. ‘Oumuamua was discovered during an ‘Alopeke commissioning run, and we’re grateful to the ‘Alopeke team for bearing with us while we overrode their time to catch this extraordinary and unprecedented event; this sacrifice enabled Gemini to help characterize GeminiFocus the peculiar properties of this exotic visitor. ‘Alopeke commissioning was, incidentally, completed, despite this interruption. Chile Early 2017B brought with it the LIGO gravi- tational wave event whose source Gemini South brought into focus, capturing early optical and infrared light from this merger of two neutron stars (see the October 2017 issue of GeminiFocus, page 7). This exciting first-time event kept staff busy for a couple of weeks and required delaying some reme- dial work on FLAMINGOS-2; this was scien- tifically well worth it, as we used the instru- ment to produce some compelling infrared spectroscopy that confirmed the nature of the event’s afterglow. See more on FLAMIN- GOS-2, below. While the first part of the semester present- ed some weather issues, the second brought much better weather, so we were able to catch up on the Band-1 programs and bring the completion rate back to reasonable lev- els. Late in the semester we received a re- markable number of Target of Opportunity (ToO) triggers: in January alone, there were 31 triggers, peaking at four on a single day. Figure 1 shows the number of nights on which Gemini South responded to a ToO re- quest per month (left: Standard ToOs; right: Rapid ToOs). Most of the variation, and in particular the end of the semester bump, April 2018