Queue Scheduling

How does the queue work? What are the priority algorithms?

The MMIRS queue software is a wrapper around the AstroPlan and astropy modules.

The queue software is re-run every morning, with new input on which fields have already been observed and which are still to be observed.

In the software, there are a few boolean checks on the observability of every field. These include airmass (set to a maximum value of 2.5), rotator angle (set by the rotator limits of the instrument; not relevant for imaging), altitude (a minimum of 20 degrees with a maximum of 88 degrees), and Moon separation (wavefront sensing in the optical requires that your object be at least 15 degrees away from the Moon). We generally begin and end observations (or set up for observations) at Nautical Twilight.

There are also three possible variable constraints that the queue software uses to decide the priorities. The variable constraints are: the ratio of time charged to a program over the total allocated time for that program (TimeAllocationConstraint), how far a target is from the meridian (MeridianConstraint, prefers lower airmass and ideally better data quality), and PI priority (PIPriorityConstraint).

How big are the individual observing blocks?

Currently, observations are divided into two-hour-maximum observing blocks (automatically created by the queue software). Multiple two-hour observing blocks are used to fill the requested time for a target.This typically makes a target easier to schedule than would a single longer observing block. It increases the chance that at least part of the requested time for a target will be observed. It also allows the observing block to be scheduled later in the night. Finally, it allows the scheduler to compare the priority of this observing block with other observing blocks more often as observing continues.

How will I know what objects from my program have been observed?

You will be able to check on the progress of your program by logging into the MMT Scheduler at any time. Emails alerting you to observed objects typically are sent the morning following the observation.

Can I be there while my data are acquired?

Covid protocols do not allow on-site observers presently. Due to the fact that the queue software is re-run each morning, we cannot guarantee that your program will be in the queue on any particular night.

How can I get my raw data? Can I look at it during the run?

Data are available at any time in the same area where you uploaded targets. If you have any issues, you can contact the Smithsonian Telescope Data Center (TDC) by emailing tdchelp@cfa.harvard.edu

Do I reduce the data myself? How do I do that?

There is a publicly available pipeline and an accompanying published paper. See https://bitbucket.org/chil_sai/mmirs-pipeline/wiki/Home for the latest pipeline, and https://arxiv.org/abs/1503.07504 for the paper. Most mask and long-slit MMIRS data are reduced by an automated pipeline. If for some reason your data are not reduced within a few days of observations, you can contact the TDC.

Why didn’t I get all the observations I asked for? Why didn’t I at least get all my priority 1 objects?

There could be a few reasons why you didn’t get all the data that you requested.

Weather. Approximately one-third of scheduled observations are lost due to clouds, high humidity, or other weather factors. This weather loss currently is shared more or less evenly over all the programs in the queue. Wind speed and direction may make it desirable to observe an object that allows pointing away from the wind. This could mean a priority 2 object gets observed before a priority 1 object.

Facilities Issues. A very small percentage of time each semester (typically <2%) is lost to telescope, building, instrument, or other facility problems. While small on the timescale of several months, an 8 hour loss of time could make a significant dent in a queue program over the course of a 7-10 day run.

Faint targets. If you are looking at very faint targets and a test exposure by the queue observer reveals no signal to noise, they may choose to pass on your object (temporarily) until they can receive more information about finding the target. You can plan ahead and submit nearby bright offset stars to the database to help locate your object, along with finder charts. Searching for your object, whether or not it is found, does get charged to your time allocation.

Slit Masks. There are 9 slots available for masks. If the total number of masks requested for the observing run is greater than 9, a mask change will take place during the observing run. This takes a full dawn-to-dusk time period. It may be that a lower priority target requiring a slit mask cannot be observed if there are, for example, weather losses followed by a mask change which removes the mask needed for the observation. Which masks are put in during the change is decided by staff after an evaluation of the progress of the programs up to that point.