Participation in this program is open to the following categories of institutions and organizations:
Each proposal must have one, and only one, Principal Investigator (PI). Any other individuals who are actively involved in the program should be listed as Co-Investigators (Co-Is). The PI is responsible for the scientific and administrative conduct of the project and is the formal contact for all communications with the CXC.
Proposals by non-U.S. PIs that
have one or more U.S. Co-Is who require funding must designate one of the U.S. Co-Is as the “Administrative PI”.
(Note:
This section establishes the observing policy for Chandra. This policy reviews and confirms the distribution of observing time among the Guaranteed Time Observers (GTOs) and General Observers (GOs), establishes guidelines for the resolution of conflicts between and within these groups, and sets guidelines for the distribution of observing time and data.
With certain exceptions, all General Observing data awarded either to GTOs or to GOs will be proprietary for one year beginning when the data are made available to the observer. For fragmented “Long Duration” observations, the one-year period for each target begins when 90% of the data have been made available to the observer.
Data from unanticipated Targets Of Opportunity (TOOs)
and other use of Director’s Discretionary Time may be proprietary for limited
periods – no more than three months – before they are placed in the public
archive. Calibration data scheduled and obtained by the
Data from X-ray Visionary Projects (XVP) will not be proprietary.
Distribution between GO and GTO - Scientific observations commenced approximately 2 months after launch. X-ray data obtained during these first two months were considered calibration data and were placed directly into the public archive. Currently, 2450 ksec of observing time per cycle is allocated to GTOs.
Distribution among GTOs -
In Cycle 14, the GTOs comprise the following: Four Instrument Principal
Investigators (IPIs) for the Advanced Imaging Spectrometer (ACIS), for the
High-Resolution Camera (
|
LETG IPI |
0.5 share |
0.5 share total |
|
HETG,
ACIS, and |
1.0 share each |
3.0 shares total |
Target selection will be carried out in a sequence phased with the timing of the CXC Call for Proposals. Target selection begins with the GTOs specifying targets that over-subscribe the GTO time available. Any GTO-GTO conflict at this point shall be resolved by the GTOs. In the event that a resolution is not achieved, the GTOs shall write proposals in accordance with the CfP. After the GO proposals are received, GO-GTO conflicts are identified. In response, GTOs may either (i) replace a conflicted target with an un-conflicted backup target or (ii) write a proposal and let the peer review decide the conflict. Targets resulting from peer review of the responses to the CfP will be added to the set of un-conflicted GTO targets to form the complete approved target list.
GTOs must submit proposals for observing time if there are GO or other GTO proposals for the same target. GTOs are guaranteed to receive their observing time in accordance with Section 3.2.1.3 but cannot reserve targets in advance of the CfP.
All conflicts (GO-GO, GO-GTO, or GTO-GTO) are decided as part of the peer review process with selection based on scientific merit.
Large Projects (Section 4.2) are those that are designated as such by the proposer and that require 300-999 ksec observing time, whether long-duration observations of single targets or shorter duration observations of multiple targets. Large Projects are encouraged. An estimated 4 Msec of observing time will be allocated for Large Projects in this cycle.
Large Projects may be multi-cycle (Section 3.2.1.14), but cannot reserve targets beyond the time and cycles proposed.
An X-ray Visionary Project proposal (see Section 4.3) should describe a major, coherent science program to address key, high-impact, scientific question(s) in current astrophysics, must require 1-6 Msec of observing time and may be multi-cycle (Section 3.2.1.14). An estimated 7 Msec of observing time will be allocated to 2 or more X-ray Visionary Projects in this cycle.
X-ray Visionary Projects must be proposed to be completed within the time span covered by this CfP and cannot reserve targets beyond that time. Given the limitation on observing as a function of pitch angle (Section 5.2.8), the total observing time of XVP targets at ecliptic latitudes > 60º will be limited to 2 Msec. The data obtained as part of an XVP will have no proprietary time.
There are two categories of Targets of Opportunity: Those that are proposed and selected through peer review (Pre-Approved); and those that simply occur and have been brought to the attention of the Director of the CXC, who may reschedule Chandra to obtain the appropriate observations in the best interest of the scientific community.
Pre-Approved TOOs
A proposed
Unanticipated TOOs
Data obtained from an unanticipated
All GO time allocations will be subject to peer review.
All GTO targets with conflicts will be subject to peer review, consistent with the provisions of Sections 3.2.1.3, 3.2.1.4 and 3.2.1.6.
For this Cycle, 700 ksec of observing time is reserved for Director’s Discretionary Time. This allocation includes unanticipated TOOs.
The number of time-constrained observations accepted in any Cycle will be limited to 15% of the total with quotas for the various classes of constraints (Section 5.2.8). New or additional constraints may not be imposed by the observer after the proposal deadline. Please note that an observation is defined as a single approved exposure of a target (see Section 3.2.3.1 also). Monitoring observations are counted based on the number of repeat visits. Long observations (>90 ksec) will be divided into several 90 ksec-long observations for the purpose of counting constraints.
Information
on the periods of time when Chandra observations
are allowed due to passage beyond the earth’s radiation zone are provided at http://cxc.harvard.edu/proposer/orbits.html.
Proposals for time-constrained observations that span more than one cycle may request time in up to 3 cycles. A maximum of 2 Msec of Cycle 15 and 1 Msec of Cycle 16 observing time may be allocated to such proposals in Cycle 14. Proposals must request time in Cycle 14, must justify the requirement for multi-cycle observations and must justify the allocation of time across the multiple cycles. The peer review reserves the right to recommend only those observations proposed for the current cycle.
3.2.2 Procedures Concerning TOOs and DDTs
The
deep orbit of Chandra permits
reasonable access to any
Requests
either to initiate a Pre-Approved
The
response to a
TOOs generated by a peer
review-approved proposal are those where time is allocated to the proposal, but
the time is unscheduled. To initiate the scheduling process, the investigator
is required to specify in the
A request for an unanticipated
If the proposed observation is accepted, the CXC will create a new timeline as soon as possible. Some negotiation between the observer and the CXC may be necessary to achieve the optimum blend of response time and minimum impact on the rest of the schedule.
General
requests for DDT must follow the same procedure as required for an
unanticipated
The following 4 exceptions are identified:
1)
2) For observations (unique sequence number) greater than 200 ksec, any remaining time exceeding 20 ksec will be scheduled even if the GTI to approved time ratio exceeds 90%, provided constraints allow.
3) For observations less than 5 ksec, targets will be observed only once and the observation will be considered complete regardless of the GTI achieved unless a spacecraft anomaly causes the entire observation to be missed.
4) For observations with less than 2 ksec remaining, no additional time will be scheduled even if the 90% GTI to approved time ratio has not been achieved.
Items 3 and 4 are intended to avoid additional short exposures with their relatively high fractional overhead (inefficient use of Chandra). Item 4 assures that observations between 5 and 20 ksec get at least 60% of their approved time (for 5 ksec approved) with a sliding scale assuring that at least 90% is achieved at 20 ksec approved time.
Note: The proprietary time begins when the observation is “complete” according to the above rules.
Data can be lost (or overwhelmed) because of occasional episodes of very high background. If the principal target was a point source and the background is ≥ 10 times nominal for ≥ 50% of the observation, the target may be observed again for a period of time equal to the amount of time lost due to the high background. If the target is extended and the background increase is ≥ 5 times nominal for ≥ 50% of the observation, then another observation may be scheduled to replace the amount of time lost due to the high background. We realize that application of these limits is somewhat arbitrary. The intent is to only schedule additional observations if the scientific objectives were not achieved due to the high background. If “space weather” only causes some deterioration in data quality, the observation is considered complete.
Although the CXC monitors space weather, there is no real-time contact with the Chandra X-ray Observatory so high background periods cannot be avoided. Ultimately, it is the observer’s responsibility to determine if the data require another observation according to the criteria above. An application for an additional amount of time on target should be made to the CXC Director. Providing a plot of the background counting rate vs. time and a short table with the integration time at different background levels is required.
Telemetry saturation produced by the target and/or other sources in the field-of-view are the responsibility of the observer. The unique case of a previously unknown transient appearing in the field-of-view will be handled case-by-case.
Science proposals from outside
the
The Chandra data archive is open to the public; to obtain data of
interest to his/her project, an interested researcher need only access the CXC website
(http://cxc.harvard.edu)
or
contact the
Proposals submitted to the CXC will be kept confidential to the extent allowed by the review process. For accepted proposals, the scientific justification section of the proposal remains confidential but other sections become publicly accessible, including PI names, project titles, abstracts, and all observational details. The remainder of the approved proposals, and the entirety of proposals not selected, will remain confidential.
All CXC and visiting personnel who will be handling or reviewing the proposals as part of the review process will be fully informed of the confidential nature of the proposals. They will be required to sign a non-disclosure agreement, agreeing to treat information in the proposals as confidential and not to disclose it or use it in any way beyond that needed for the review process itself. All copies (electronic and hardcopy) of the proposals distributed as part of the review process will be destroyed once the process is complete.
Proposals for new observations that duplicate existing Chandra observations will not be accepted unless scientifically justified. It is the proposer’s responsibility to ensure that he or she does not propose for observations of the same target with the same instrument and comparable observing time to one already in the Chandra Observing Catalog or that such a request is explicitly justified. For targets previously observed in the X-ray band, particularly those observed by XMM-Newton, the proposal should address the specific need for the addition of Chandra data to accomplish the proposed scientific investigation. Previous observations may be checked using, for example, HEASARC W3Browse: http://heasarc.gsfc.nasa.gov/docs/HHP_heasarc_info.html.
Previous observations may also be checked using the
The review panels will be provided with a list of previous Chandra/XMM-Newton/Suzaku X-ray observations of proposed targets. Information on the various ways to access the Chandra Observation Catalog may be found in Section 6.1.3.
As part of the proposal and corresponding budget for a Chandra investigation, proposers may request funding support for correlative observations at other wavelengths beyond the joint observations described in this solicitation (Section 4.5). Funding for such correlative studies will be considered only when they directly support a specific investigation using Chandra. Unless there are exceptional circumstances, such as a CXO/NOAO or CXO/NRAO joint proposal or some archive or survey proposals, funding for ground-based supporting observations should not exceed 10% of the total request.
