Agreements for Joint Observations with the NRAO were made before the observatory was split into multiple observatories.  Access to the Joint Observing program will continue for the GBT at least for semester 19B.  Since the arrangements were made through the NRAO, the documentation below does not directly mention the GBO.

In previous semesters, the community has had the opportunity to propose for observing time on NRAO facilities through a joint program with the Chandra X-ray Observatory. For Chandra, proposals must be for observations that require both Chandra pointings and NRAO observations to carry out a scientific investigation. The NRAO has allocated up to 3% of the open skies observing time on the VLA, the VLBA, and the GBT for Chandra joint proposals.  The Chandra Cycle 21 deadline was 14 March 2019 and will cover January 2020 to January 2021.  See the Chandra Call for Proposals for details.

Starting with semester 2016A, proposals to the NRAO can request time on Chandra, to be awarded on the recommendation of the NRAO TAC and approved by the NRAO Director. Up to 120 ksec will be made available to NRAO proposers annually.

Chandra as Primary Observatory: NRAO observing time awarded through the Chandra Cycle 21 review will be implemented during the 2020A and 2020B observing semesters. The award of time on NRAO facilities will be subject to approval by the NRAO Director, after technical review and a nominal review by the NRAO TAC to avoid duplication of programs. The important additional criterion for the award of NRAO time is that both the Chandra and the radio data are required to meet the science goals of the project. Proposed NRAO and Chandra observations are not required to be coordinated or simultaneous. Under this agreement, NRAO time will only be awarded in conjunction with new Chandra observations (and should not be proposed for in conjunction with an Archival Research or Theory Proposal).

NRAO as Primary Observatory: Chandra time awarded through the NRAO TAC will be implemented during the course of Chandra Cycle 21.  Proposals submitted to the NRAO requesting Chandra time must indicate that the proposal is joint with Chandra. Furthermore, the proposal must briefly justify for each target the number of kiloseconds, and the Chandra instrument and observing mode requested. The important additional criterion for the award of Chandra time is that both Chandra X-ray and radio data are required to meet the science goals of the project. Proposed NRAO and Chandra observations are not required to be coordinated or simultaneous. Programs requesting Chandra time will be subject to basic technical review prior to the NRAO TAC meeting. No Chandra TOOs can be awarded through this program.

The PIs of successful programs with Chandra as the primary observatory will be contacted by NRAO science operations. Successful PIs of programs with NRAO as the primary observatory will be contacted by Chandra science operations. Successful proposers will submit Chandra Cost proposals at the standard deadline. Funding will be available to US investigators to support Chandra data reduction.