Main Proposer Page

What's New in Cycle 22

The CXC has released an updated Cycle 22 Call for Proposals in Feb. 2020. A summary of changes is available.

Bright Sources

Observations of extremely bright sources (> 5 Crab) carry significant risk to the detectors and will only be considered in exceptional cases. Proposers who wish to observe sources that are known to reach these flux levels must contact the CXC Helpdesk before submitting a proposal.

Resource Costs, UPDATED FEBRUARY 2020

In Cycle 22, 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 32,000. 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 22 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 UPDATED FEBRUARY 2020

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 UPDATED FEBRUARY 2020

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. A maximum of 2.5 Ms of observing time on targets situated above 55 deg or below -55 deg ecliptic latitude will be available at the Cycle 22 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, NEW IN FEBRUARY 2020

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).



What's New in Cycle 22 (Dec release)

Bright Sources

Observations of extremely bright sources (> 5 Crab) carry significant risk to the detectors and will only be considered in exceptional cases. Proposers who wish to observe sources that are known to reach these flux levels must contact the CXC Helpdesk before submitting a proposal.


Resource Costs

We are developing a new metric accounting for the complexity/ease of scheduling each non-TOO observation which will encompass most of our previous constraint-related allocations: Resource Cost (RC). See Section 4.3 of the CfP for more details.

At the time of writing (December 2019) the RC metric is being finalized and we anticipate that it will be ready in February 2020. Proposers will be informed by 15 February 2020 if the RC metric is not ready for use. If the RC metric is not implemented the old constraint categories will be used. Assuming that the new RC metric is implemented, proposers will be able to estimate RC associated with their proposed targets via CPS no later than 15 February 2020. Examples of RC for different targets (e.g. high ecliptic latitude, a simple window constraint etc.) will be posted on the Cycle 22 Proposers webpage. PIs of proposals that are submitted prior to the RC algorithm becoming available will be contacted with estimates of the total RC for their proposal should they wish to update their proposal based on the new RC.

Prior to Cycle 22, constraints were classified into "easy", "average" and "difficult" categories. If the new RC metric is implemented by 15 February 2020 these categories will no longer be used in Cycle 22.


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 22 and beyond. Coordination with ground-based observatories must now be entered as a constraint.


Roll and/or offset adjustments after LTS placement

Some proposers ask to adjust the roll and/or pointing of an observation once the observation is placed in the Long Term Schedule and the nominal roll angle known. This request is frequently made to ensure an extended target is optimally positioned on the detectors. From Cycle 22, these requests must be specified on the CPS forms. Observations constrained in this way will incur a higher RC (or a constraint if RC are not implemented).


TOO Follow-ups

From Cycle 22, all TOO follow-up observations (observations following an initial trigger observation) will count as TOOs for the purposes of counting triggers at the peer review - see Section 4.6 of the CfP 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 of the CfP. The total number of triggers (all response categories) has not changed.


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. A maximum of 2.5 Ms of observing time on targets situated above 55 deg or below -55 deg ecliptic latitude will be available at the Cycle 22 peer review. Proposers are encouraged to favor low ecliptic latitude objects unless key science goals require high latitude targets. See Section 4.5 of the CfP for details.