Mid-Cycle GO Proposals must meet the following prime criteria:

1. Proposers must provide an explanation of why the proposal could not have been submitted in response to previous Calls for Proposals: for example, the target may have been identified subsequent to the most recent relevant proposal deadline. 
2. Proposers must provide a clear description of the scientific urgency of these observations and why they should be executed in the present cycle. 

Proposers can see the past MidCycle programs that have been approved.  This list is updated after the results of each Review have been made public.  

Proposals should be submitted via the Astronomer’s Proposal Tool (APT) as type GO, using the Mid-Cycle template for the pdf attachment. Upon completion of your Mid-Cycle submission, your program will be transferred to the STScI for processing. If you run into problems submitting an Mid-Cycle Request, Contact the STScI HST Help Desk web: https://hsthelp.stsci.edu for a quicker response, or send email to help@stsci.edu for investigation/resolution.

Proposals for Mid-Cycle time must be sufficiently detailed for adequate evaluation, comparable with proposals submitted for the regular observing cycles as described in the current Call for Proposals.  Among other things,

• Both the proposed observations and the use of Mid-Cycle time must be justified explicitly,
• There must be an adequate description of how the proposed observations relate to the current state of knowledge,
• And the proposed observations must be described in sufficient detail to allow technical evaluation.

Mid-Cycle GO proposals will have the following characteristics:

• Proposals are limited to requesting no more than 15 orbits; 
• Observations should have minimal constraints to maximize scheduling flexibility-- Target of Opportunity proposals may not be submitted as Mid-Cycle Proposals;
• Observations taken for accepted programs will have a proprietary period of no more than 3 months;
• Proposals may request only HST time - joint proposals are not permitted;
• Proposers may apply for all available instruments. Proposals must be compliant with the technical restrictions described in the most recent Call for Proposals.
• Page limits are the same as Regular GO Small proposals.

Please also note that Mid-Cycle proposers may select any of the HST Cycle 27 Special Initiatives for their proposal. JWST Preparatory Observations will, by default, not have a proprietary period (default of zero months).

Review Process and Schedule

Members of the STScI Science Policies Group will undertake an initial review of GO Mid-Cycle proposals to determine whether the proposals meet prime criterion #1. Proposals that do not meet that criterion will not be distributed for further review; the Principal Investigator will be informed of that decision, and is free to submit the proposal at the next standard cycle deadline. Re-submissions of rejected past cycle proposals will be rejected automatically.

Mid-Cycle proposals will receive scientific review by members of the community who have contributed to recent HST TAC reviews. Each proposal will be distributed to four reviewers.

Mid-Cycle proposals may be submitted at any time. Proposals received by January 17, 2020 will be considered for implementation in the March 1, 2020 to September 30, 2020 time-frame.

Reviewers are required to address the following issues:

1. The scientific merit of the proposed investigation and its potential contribution to the advancement of scientific knowledge – grade 1-5;
2. The program’s importance to astronomy in general – grade 1-5;
3. The scientific urgency of the observations and their suitability for a Mid-Cycle proposal – grade 1-5;
4. The program science goals can only be achieved by observations with Hubble Space Telescope – yes/no.

Grades are as follows:

1. - Excellent
2. - Very Good
3. - Good
4. - Fair
5. - Poor

Reviewers are also required to provide brief text feedback on the strengths and weaknesses of the proposal, and a rationale for their grades.

The STScI Science Policy group will collect the reviews and rank order the proposals. The Director will make the final selection of proposals to be awarded time.