HST Call for Proposals for Cycle 25
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Hubble Space Telescope Call for Proposals for Cycle 25 > Chapter 3: Proposal Categories > 3.5 Joint HST-Chandra Observing Proposals

3.5
If your science project requires observations from both HST and the Chandra X-ray Observatory, you can submit a single proposal to request time on both observatories to either the HST Cycle 25 or the Chandra Cycle 19 review. This avoids the “double jeopardy” of having to submit proposals to two separate reviews. A description of past HST joint programs is available on the HST Joint Programs webpage.
Joint HST-Chandra proposals are of two types:
Regular HST-Chandra Proposals: By agreement with the Chandra X-ray Center (CXC), STScI will be able to award up to 400 kiloseconds of Chandra observing time. Similarly the CXC will be able to award up to 100 orbits of HST time to highly rated proposals awarded Chandra time in its TAC process. The only criterion above and beyond the usual review criteria is that the project must be fundamentally of a multi-wavelength nature, and that both sets of data are required to meet the science goals. It is not essential that the project requires simultaneous Chandra and HST observations. Chandra time will only be awarded in conjunction with new HST observations (and should not be proposed for in conjunction with an AR or Theory Proposal).
Large HST-Chandra Proposals: By agreement with the CXC, STScI will be able to award an additional 600 kiloseconds of Chandra observing time for Large joint programs. These programs are defined as requiring at least 75 orbits of HST time and at least 400 ksec of Chandra observations. Similarly, CXC will be able to award up to 150 orbits for Large Programs submitted to the Chandra TAC. As with Regular HST-Chandra Proposals, the only criterion above and beyond the usual review criteria is that the project must be fundamentally of a multi-wavelength nature, and that both sets of data are required to meet the science goals. It is not essential that the project requires simultaneous Chandra and HST observations.
Of the 1 Msec of Chandra observing time that can be awarded in the HST review, only approximately 15% of the observations may be time-constrained. In addition, only one rapid ToO can be awarded (less than 20 days turn-around time). A Chandra ToO is defined as an interruption of a command load, which may include several predictable observations within that one-week load. HST Cycle 25 proposers should keep their Chandra requests within these limits.
Regular proposals for combined HST and Chandra observations should be submitted to the observatory that represents the prime science (not to both observatories). Large HST-Chandra proposals (or Very Large Programs, as CXC defines them) may be submitted to either, but not both, observatories. STScI reserves the right to disallow HST observations that duplicate those approved via any joint program unless the duplications are justified in the original proposals. The Chandra Cycle 19 deadline is March 15, 2017 at 6 pm EDT. While there is multi-wavelength expertise in the review panels for both observatories, typically the HST panels will be stronger in IR/optical/UV science and the Chandra panels in X-ray science.
Establishing the technical feasibility of the Chandra observations is the responsibility of the PI, who should review the Chandra documentation or consult with the CXC. A description of the technical information that should be included in the proposal is given in Section 9.4.1. For proposals that are approved by HST, the CXC will perform detailed feasibility checks in Chandra Cycle 19. The CXC reserves the right to reject any previously HST-approved observation that proves infeasible, impossible to schedule, and/or dangerous to the Chandra instruments. Any Chandra observations that prove infeasible or impossible could jeopardize the overall science program and may cause revocation of the corresponding HST observations. Duplicate Chandra observations may also be rejected by the CXC.
Joint HST-Chandra Proposals must be identified in the ‘Special Proposal Types’ section of the proposal (see Section 8.10). Also, you must include technical information about the Chandra observations in the ‘Coordinated Observations’ section of the proposal (see Section 9.4.1).

Hubble Space Telescope Call for Proposals for Cycle 25 > Chapter 3: Proposal Categories > 3.5 Joint HST-Chandra Observing Proposals

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