(NEW!) AEON Time Critical Mode on SOAR

Introduction

Las Cumbres Observatory, which provides scheduling for SOAR’s AEON queue mode, offers a couple of modes suitable for high-priority time-domain observations. These correspond roughly to SOAR’s two target of opportunity (ToO) modes.

• Time-critical observations can be submitted at any time, and are executed when (a) conditions permit and (b) any on-going observation finishes. “Conditions” in this case means the instrument is available, lunar phase is acceptable, it’s not horribly cloudy, and the target is above a minimum elevation (less than a maximum airmass). This can be thought of as equivalent to “delayed activation” targets of opportunity in SOAR’s ToO terminology.
• Rapid-response observations take place as soon as possible, providing conditions are met, and will abort on-going observations if necessary. They can be thought of as equivalent to “instant activation” targets of opportunity. As a practical matter, the second type of observation is only meaningful if the target is observable at the time the observation is submitted; a time-critical target submitted in the afternoon will be executed as quickly as a rapid-response target submitted at the same time.

SOAR has already enabled time-critical observing for all approved target of opportunity programs. This means that they can trigger through the Las Cumbres portal during AEON nights, if their observations are compatible. They then don’t need to supply an observer and the data-taking is integrated into the AEON queue. If they have incompatible observations, they interrupt AEON as on any other night, and queue operation resumes when they are done. What we are now enabling is an additional time-domain mode in which only AEON time-critical observations are enabled (plus, if desired, regular queue and classical time). This would be intermediate between regular ToO proposals and standard AEON queue proposals.

Rationale

There are time-domain programs where observers need a moderately dense observing cadence, but can be satisfied by the typical AEON cadence of every 5 days or so. In some cases, the important dates are known (e.g., solar system objects at perihelion or close approach) and in others they are not (e.g., bright supernovae). The advantage of offering this mode is that it is not disruptive in the way that ToO mode can be, and it potentially enables interesting science. There are going to be cases where data are needed every night (e.g., BNS mergers, young supernovae) and only target-of-opportunity mode will work. Also, ToO mode allows use of almost all instruments, whereas AEON supports a subset of observing modes – though these comprise most configurations of interest. Additionally, if the program only comprises time-critical AEON observations (and possibly other AEON observations), the PI does not need to supply a trained observer, and can simply make submissions through the Las Cumbres portal. This is less of a burden on the PI and on SOAR support staff. It may be a particular benefit to a PI who is not part of a big observing team.

Implementation

Time-critical observations obviously get preference, which means that they edge out regular AEON programs and benefit from available clear weather. In order to compensate for this and not penalize the regular AEON programs, any time-critical program approved by a partner would require the partner to contribute 130% of the approved time to the queue time pool. Thus, if a partner approved 20 hours of time-critical programs, they would need to contribute 26 hours (2.6 nights) to the pool of AEON time. This factor more or less compensates for time lost to weather and technical issues.

Second,  as we roll out this mode we will limit approved programs to ~<10h hours of time-critical observing. The PI could ask for additional time as regular AEON time if they were granted enough time. Taking the example of a solar system close approach, they might ask for 6 time-critical hours to cover the 2 weeks around close approach, and another 10 regular hours to get less frequent observations before and afterward. A justification for the mode should be included, it is not intended for people who just want high priority.

It is up to each partner whether to offer this mode. Some may choose to do so, and others may not. So if only NOIRLab offers it, the other partners will not see their observing time affected in any way. Anyone who applies for time in this mode should identify the amount of time requested as an AEON queue "run" (in NOIRLab terminology); any request for regular AEON time would be another "run".