NICER Policy for Target of Opportunity Requests

NICER is committed to maximizing science yield in time-domain X-ray astrophysics. Building on real-time data acquisition and commanding capabilities, pointing agility, and increasing automation, NICER's dynamic operations enable rapid response to transient and otherwise unpredictable phenomena.

The NICER operations team aims to react promptly to all time-sensitive requests for "target of opportunity" (ToO) observations, such as for unfolding astrophysical events or coordination with dynamically scheduled observations at other facilities. ToO requests, which must be submitted via the online form, may originate from within the NICER team, from a Guest Observer (GO) with an approved peer-reviewed proposal, or from the general community.

In keeping with the goal of maximum science return – in particular, to avoid missed opportunities – the NICER operations team evaluates, and may choose to act on, all ToO requests as they are received, whatever their origin. NICER staff also endeavor to deliver "quick look" data to ToO requesters, on a best-effort basis; in any case, all non-GO data enter the public NICER archive within two weeks of acquisition.

There are special implications of this policy for GO ToO investigations. It is the GO investigator's responsibility to notify NICER, via the online form, that ToO triggering criteria have been satisfied and to request that observations be scheduled. It is possible, however, that an independent ToO request for the same target will have already been received, approved, and executed, or that an existing monitoring program for the same target will have resulted in a recent set of observations. In such cases, implementation of the GO trigger will take place at the next reasonable observation scheduling opportunity. Data acquired from any observations scheduled prior to implementation of the GO trigger will be considered "public" – i.e., will enter the public archive within two weeks, but with quick-look data likely available to any initial ToO requester. Data acquired subsequent to a GO trigger notification will be assigned to the GO project and will be subject to any exclusive-use period granted to that project.

Occasionally, an independent ToO request received after a GO trigger notification will offer enhanced science return – e.g., through coordination with another observatory or because prompt analysis of the data suggests a modified observing strategy not anticipated by the GO effort. In such cases, NICER will consider this information in planning additional observations of the ToO, and will reach out to both the GO investigator and the independent ToO requester to foster collaboration where possible.

Last Updated: March 9, 2020