3.1 Overview of Proposal Categories

HST observations can be requested with a General Observer (GO; see Section 3.2) or a Snapshot (SNAP; see Section 3.3) Proposal. A GO Program can be Small (see Section 3.2.1), Medium (see Section 3.2.2), Large (see Section 3.2.3), Calibration (see Section 3.2.4), Long-term (see Section 3.2.5), or Treasury (see Section 3.2.6). Funding for projects that do not require new HST observations can be requested with an Archival Research (AR; see Section 3.4) or a Theory (see Section 3.4.4) Proposal. An AR Program can be either a Regular AR (see Section 3.4.1) or a Legacy AR (see Section 3.4.2) Program. Proposals can also request observing time on Chandra (see Section 3.5), Spitzer (see Section 3.6) XMM-Newton (see Section 3.7), or NOAO facilities (see Section 3.8). At any time scientists can request Director’s Discretionary (DD) time for unanticipated and scientifically compelling astronomical observations (see Section 3.9). U.S. Investigators with approved proposals are strongly encouraged to submit an associated Education/Public Outreach (E/PO) Proposal (see Chapter 11).