Chandra Announcement: Cycle 23 Call for Proposals, Associated Software, and Documentation Released

[Tara Gokas]

Chandra Cycle 23 Call for Proposals Released 16 December 2020

The CXC is pleased to announce the release of the Chandra Cycle 23 Call for Proposals (CfP). The Call for Proposals, Proposers' Observatory Guide (POG), proposal planning software, and general information are posted on the "Proposer" web page at the CXC website:  http://cxc.cfa.harvard.edu/proposer/.

Proposals are due: Tuesday, 16 March 2021 at 6PM (US Eastern Daylight Time)

Hardcopy documents are available on request to the CXC HelpDesk (http://cxc.cfa.harvard.edu/helpdesk).

What's New in Cycle 23

Dual Anonymous Peer Review (DAPR)

Starting in Cycle 23, the Chandra peer review will be dual anonymous: the proposers (as usual) will not know the identity of the reviewers, but in addition the reviewers will not know the identity of the proposers. Proposers should ensure that the abstract and proposal text do not reveal the identities of the proposing team, as described in Section 7.2. Please also note that a document (not anonymized) describing the expertise and experience of the proposing team is now required for submission (the Team Expertise document, Section 7.11). The discussion of the science merits of each proposal is anonymous, but after the final rankings, reviewers are given the Team Expertise document for proposals that are above the pass-fail line. The panel may flag teams that they consider to lack the qualifications needed to carry out the proposed investigation. Such "disqualification" flags are expected to be very rare and must be agreed by a majority of the panel. The ultimate decision to disqualify a proposal is taken by the selection official. See Section 9.1 for a more detailed description of DAPR.  

Naming Conventions for Astronomical Sources

Proposers are asked to double-check that target names can be unequivocally associated with a sky position and follow the IAU specifications for astronomical sources. Please see Section 7.13.

Exclusive Use Period

In Cycle 23 and subsequent cycles Very Large Projects will not have an exclusive use  period (no proprietary time). See  Section 3.2.

Major Changes in Cycle 22 

Several major changes were introduced in Cycle 22 involving constraints, preferences, TOOs and followups, and grids. All proposers, especially those who did not submit a proposal in Cycle 22, are encouraged to review the following updates:

Resource Costs  

In Cycle 22 and subsequent cycles, a "Resource Cost" (RC) will be calculated for each proposed non-TOO target. The RC quantifies the difficulty of scheduling each non-TOO observation. The RC replaces "constraint categories" used in previous Cycles. The RC will be calculated for all non-TOO targets including those with no user-imposed science constraints.  Targets near the ecliptic poles are difficult to schedule: therefore even observations without constraints may incur a non-zero RC by virtue of its sky position.  The RC for all targets in a proposal can be calculated within CPS. There is a cap on the total RC that will be accepted at the peer review. We anticipate this to be  approximately 27,500.  See  Section 4.3 for more details.

Observing Preferences

Prior to Cycle 22, observing preferences (e.g. time windows, roll angles etc) were allowed to enhance the science return of proposed observations. Due to the increasing complexity of keeping the spacecraft within acceptable thermal limits, preferences will not be accepted in Cycle 23 and beyond. Coordination with ground-based observatories must now be entered as a constraint.

Roll and/or offset adjustments after LTS placement

Adjustments to roll and/or pointing to optimally place a target on the detector given the observation date must  now be specified on the CPS forms. Observations constrained in this way are difficult to schedule and will incur a higher RC

TOO Follow-ups

From Cycle 22, all TOO follow-up observations (observations following an initial trigger observation) will be classified as a half trigger for the purposes of counting triggers at the peer review - see  Section 4.6 for more details.

TOO Response Times 

TOO response times and the number of available triggers within each response category have changed. Please see Table 6.

High Ecliptic Latitude Targets 

Targets at high ecliptic latitude (> 55 degrees) heat the Aspect Camera Assembly and are always at a thermally unfavorable pitch angle. Approximately  2.0  Ms of observing time on targets situated above 55 deg or below -55 deg ecliptic latitude will be available at the Cycle 23 peer review. In addition, high ecliptic latitude targets will incur a higher RC than targets at lower latitudes.  Proposers are encouraged to favor low ecliptic latitude objects unless key science goals require high latitude targets. See Section 4.5 for details.

Slew Tax and slew tax for grid surveys

In previous Cycles the slew tax has been 1.5 ks for each  90 ks of observing time (e.g. a 100 ks observation is considered to be 90+10 for the purposes of assessing slew tax) . Going forward the slew tax will be based on 30 ks segments (Section 9.1.1).  This new formula also applies to grid surveys (Section 9.1.2)