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7.1     Evaluation of Research Objectives

The criteria used in the Stage 1 evaluation are listed below in order of importance.

1. The overall scientific merit of the investigation and its relevance to the Chandra science program and capabilities. This includes addressing the scientific objectives of the Chandra mission which are aligned with the NASA strategic plans. For observing proposals, the degree to which the objectives have been satisfied by one or more previous observations will be evaluated. (Section 3.5 gives instructions for obtaining information on completed and planned observations).
2. For observing proposals, the suitability of using the Chandra X-ray Observatory and data products for the proposed investigation and the need for new X-ray data beyond any already obtained; the feasibility of accomplishing the objectives of the investigation within the time, telemetry, and scheduling constraints; and the feasibility of the analysis techniques. For programs incurring a large expenditure of observatory time relative to exposure time (multiple short exposure or grid pointings), the total observatory time required will be considered. For X-ray Visionary Projects, the legacy value and the project’s ability to address key, high-impact questions in current astrophysics will also be considered. For Archival Research and Theory/Modeling proposals, the relevance to the Chandra scientific program will be considered. For Archival Research proposals, the value of any additional analysis beyond the original use of the data will also be considered.
3. The competence and relevant experience of the Principal Investigator and any collaborators as an indication of their ability to carry the investigation to a successful conclusion. Past performance in scientific research, as evidenced by the timely publication of refereed scientific papers including those on previous Chandra programs, will be considered.
4. To aid in the Stage 2 cost review, the data analysis and interpretation effort required to achieve the proposed science goals will also be evaluated by the Stage 1 peer review panels.

The peer review will be conducted using a number of panels, each responsible for proposals directed at particular scientific topics. Large Projects will be initially evaluated by the appropriate topical panel, but the final recommendation for award of time will be made by the Big Project Panel. X-ray Visionary Projects will be evaluated by the XVP panel in addition to the topical panels, but the final recommendation for award of time will be made by the Big Project Panel. The final evaluation stages of both Large and X-ray Visionary Project proposals demand that reviewers efficiently consider a significant number of proposals that may be outside their area of expertise. LP and XVP proposers are advised to bear this in mind when preparing their proposals.

7.1.1      Observing Efficiency/Slew Tax

An observing efficiency including slew and settle time is used to determine the amount of time actually necessary to accomplish a proposal. Thus, in addition to the time on target, a "slew tax" is added when accounting the observing time at the peer review. Due to orbital or thermal constraints, longer exposures are candidates for segmenting into multiple observations by Mission Planning.

The slew tax is 1.5 ksec for each target that requires less than 90 ksec of observing time. Observations requiring more than 90 ksec will be charged an additional 1.5 ksec tax per 90 ksec or fraction thereof. Thus, a proposal requesting a 210 ksec observation of one target is charged a slew tax of 4.5 kec for the purpose of the peer review. For a large set of short exposures of different targets, this slew tax can substantially increase the "cost" in terms of time needed for a project. The RPS provides a tool which, given the entered target parameters, generates an estimate of the constraint class of each target and the "slew tax" (pointing overhead) which will be added to the observing time at the peer review.

7.1.2      Grid Surveys and Slew Tax

• For a series of contiguous or nearly contiguous pointings (maneuver from one observation to the next of less than or equal to 1 degree), with no change in instrument set-up or observing mode, the slew tax for the first observation will remain 1.5 ksec, while for observations 2 through n (where “n” is explained below) slew tax will be assessed at 0.5 ksec.
• A grid of pointings will be assembled into one or more groups comprised of a set of closely spaced pointings with a maximum exposure time per group of 90 ksec, including the slew tax.
• The value of “n” is the number of observations that can be done including the slew tax without exceeding 90 ksec. Proposals requesting more than 90 ksec (including slew tax) will be assessed slew tax in several groups, the first observation of each group will be charged the 1.5 ksec slew tax.
• Proposers should set the RPS flag “Is this observation part of a grid survey?” to be “Y” (yes).

Please note that observations taken as part of a grid survey are not constrained and therefore are not guaranteed to have the same (or similar) roll angle. Proposers must also include a group or roll constraint if they wish to ensure that the individual observations have roll angles within particular tolerances. The number of constrained observations, should a grid be constrained, will be determined similarly to the slew tax calculation. Grid observations will be grouped into sets with total exposure time, including slew tax, of no more than 90 ksec and each group will be charged as 1 constrained observation, classified according to the scheme in Section 5.2.8. Please refer to the thread Slew Tax and Constrained Observations for Grids. See http://cxc.harvard.edu/ proposer/threads/slewtax for examples.

7.2     Selection

The final selection of proposals is made by the Selecting Official (the CXC Director), who notifies the PIs and the Chandra Project Office at MSFC of the results. The list of selected targets is posted on the CXC website (http://cxc.harvard.edu/target_lists/) ) and entered into the Observation Catalog.

Although some investigations may begin immediately (Archival Research, Theory/Modeling, and Joint Observing Projects), no funding will be provided until the Stage 2 Cost review is complete and the final award has been issued. As a general rule, PIs of proposals requiring new observations will not be funded until the first observation has been successfully performed and the data provided to them.

7.3     Implementation

Once an observing program is approved, the targets are transferred to the Chandra Observation Catalog (OBSCAT) and assigned a unique observation identifier (OBSID) for scheduling. Below we describe the process of observation parameter confirmation and scheduling the observations (see the Proposers’ Observatory Guide for more information). The PI is considered the primary point of contact for all matters pertaining to the science program. If a separate "Observer" is identified, they will be the primary point of contact for observation planning. The PI (and Observer if there is one) will be notified when program data are available for download.

Once the approved observations are in the OBSCAT, the CDO contacts all PIs and observers to confirm those parameters most critical for scheduling the observations. This process, known as the Initial Proposal Parameters Signoff (IPPS), includes confirmation of time constraints and preferences, target coordinates and instrument selection. Once these responses have been received and any updates completed, the Chandra Mission Planning team begin their generation of the Long-term Schedule (LTS), which covers the full observing cycle (see below). A second, detailed review of observation parameters is initiated by the Uplink Support Interface team (USINT) at the CXC and carried out by the observers. USINT contacts each observer to request a detailed check of ALL observing parameters. An observation can only be released for final scheduling in the Short-term Schedule (STS, see below) once this second check has been completed.

The Chandra Mission Planning and Operations teams at the CXC produce a mission timeline using a two-part process. First, for the entire period covered by this CfP, a long-term schedule (LTS) is generated with a precision of about a week. The LTS is published on the CXC web page: (http://cxc.harvard.edu/longsched.html.). Updated LTSs are generated regularly, as needed, in response to TOOs and other timeline changes. Targets are scheduled in the LTS to achieve maximum efficiency in the observing program within the operational constraints of Chandra. Unconstrained observations are scheduled to produce the highest observing efficiency. Unconstrained targets with relatively short exposure times, totaling a substantial fraction of the observing time, are held in a pool from which they can be selected for use in short-term scheduling. Second, about three weeks prior to the anticipated execution of the observations, a short-term schedule (STS) is produced. The STS is used for the automatic generation of the required spacecraft commands. The STS, including slew times, pointing direction, guide stars, roll angles, etc., is reviewed and finalized approximately one week in advance of execution, at which time it is published on the CXC web page:  (http://cxc.harvard.edu/target_lists/stscheds/.

The CXC will make its best effort to schedule all approved observations. All approved non-TOO observations that are not scheduled, or that were scheduled but not successfully executed, will automatically be rescheduled within the current observing cycle or carried over into the next observing cycle. However, approved TOO observations that are not triggered will not be carried into the next cycle; they must be proposed for again. The official changeover date between cycles will be published on the CXC website.

If observations have to be cut short because of unforeseen circumstances, the following criteria will determine whether the target will be scheduled for additional observing time. For observations of 5 ksec or greater, the observation will be considered complete if 90% or more of the approved exposure time was obtained. For observations less than 5 ksec, only one best-effort pointing will normally be attempted. (see Section 3.2.3 for more details).

For information on proprietary data rights, see Section 3.2.1.2. A PI may waive or shorten the proprietary period, and this is customary for observations intended to benefit the general community. The CXC will ensure that the proprietary rights of other PIs are not violated by such an early data release.

7.3.1      Possible Early Observation of Targets

Efficient and safe operation of the Observatory requires substantial flexibility in target selection.  A result of this requirement near the end of a cycle may be the need to advance some observations selected by peer review before the normal beginning of the next cycle. In such cases the relevant observers will be contacted by the CXC to request an early detailed check of observing parameters, possibly at short notice.