Feb 7th, 2008

In order to help us execute your LGS program, I would like to give you all a bit of information about how LGS operations work at Gemini North.

For each of your targets, we have to get clearance from Space Command to propagate the laser. Space Command has very recently changed how they derive these clearance time windows. With their new format, these clearances change every night of an LGS run, and few of the clearance windows are significantly longer than two hours.

For Space Command to give us information on the clearance windows, we send Space Command lists of LGS targets for the upcoming run. These target lists are prepared approximately a week before each LGS run. To have your target included in this list, your observations have to be "ready" in your phaseII. The only exceptions are Standard Target of Opportunity programs. However, if you do know your Standard ToOs ahead of time, I encourage you even in that case to help us by getting the observations defined early.

The dates for when the LGS target lists are prepared are now on our public web page, on the phaseII instructions page:

www.gemini.edu/sciops/OThelp/otSpecialInstructions2008A.html

For example, for the upcoming February LGS run, the target list will be prepared Feb 15, from "ready" observations at that time.

In order to make optimal use of the clearance windows it helps us if you, your NGO and CS keep the following things in mind as you finalize the phaseII definitions:

• limit use of LGS on calibration targets
• either split long science observations into blocks of roughly 1.5h or less, or structure the observations such that it is clear where they can be split

Your program will not be penalized for any extra time used for additional acquisitions of your targets due to this splitting of observations.

I realize that a lot of phaseII definitions are already in place, and that in some cases we (Gemini staff) will have to work with you to modify some of your observations to make scheduling easier.

Thanks for your time and let me know if you have any questions.

Inger Jorgensen
Gemini North Head of Science Operations