1.2 New and Important Features of Cycle 16

• Cycle 16 will start in July 2007 and is likely to be shorter than the usual duration of one year. NASA is in the early stages of planning for a Servicing Mission 4 (SM4) to the Hubble Space Telescope, subject to final authorization by the NASA Administrator. Current plans are to schedule SM4 during the nominal Cycle 16 period, potentially as early as January 2008. Cycle 16 will terminate at that point. Cycle 17 will commence with the new suite of instrumentation, including Wide Field Camera 3 (WFC3), the Cosmic Origins Spectrograph (COS) and, possibly, a refurbished Space Telescope Imaging Spectrograph (STIS). An attempt to refurbish STIS will be made on a best effort basis.
• ACS suspended operations on 19 June 2006 due to a problem with the Side 1 electronics. Operations were switched to the Side 2 electronics on 2 July 2006. ACS also suspended on 23 September 2006 due to a fault in the High Resolution Camera electronics box. Observations resumed with the Wide Field Camera on 1 October 2006. The HRC returned to service on 10 October. All three cameras are operating nominally and will be available in Cycle 16.
• HST switched to two-gyro operations on 29 August 2005, and will continue to operate in this mode in Cycle 16. On-orbit tests indicate that there is little degradation in image quality, and hence scientific performance, while the overall observing efficiency is generally degraded by less than 5%; however, there are significantly tighter constraints in scheduling individual observations, and observers should use the information in the Two-Gyro Handbook and the web-based tools on the Two-Gyro Web Page or the APT (the Astronomer's Proposal Tool; see Section 1.4.6) to check the viability of their observing strategy. Full details of two gyro operations are given in the HST Two-Gyro Handbook.
• A new type of GO program, Survey Proposals, has been introduced in Cycle 16 in response to requests for an alternative option for programs that are statistical in nature. Survey proposals are like SNAP proposals in that they allow a large pool of candidate targets to be specified from which a subset will be selected for execution. However, Survey proposals are GO programs, which will be ranked against Regular GO programs in peer review and, if selected, will be assigned a guaranteed number of orbits. Therefore, while specific targets are not guaranteed, Survey proposals are appropriate where it can be demonstrated that a fixed number of targets must be observed to accomplish the science goals of the proposal (see Section 3.2.3 for full details). The observations cannot require special scheduling constraints(e.g., CVZ, timing requirements, or telescope orientation requirements), and, to enhance scheduling efficiency, are limited to durations of less than 48 minutes per orbit. Survey proposals are subsidized at a higher rate than other GO proposals in the time assignment process (see Section 6.1.1).
• Snapshot proposals are limited to less than 40 minutes duration (including target acquisition) for each target. Scientific programs that require longer duration exposures should be submitted as GO Survey programs.
• Joint HST-Spitzer proposals have been expanded to include a new category, Coordinated HST-Spitzer proposals. This category, equivalent to Large/Treasury GO programs, accommodates proposals that require substantial allocations of time on both HST and Spitzer. These proposals will be considered by a Joint HST-Spitzer TAC, comprised of members of the separate HST and Spitzer TACs. Proposers intending to submit a Coordinated HST-Spitzer proposal must submit a non-binding Notice of Intent by 1 December 2006 (see Section 3.7.2)
• Proposers submitting multi-cycle proposals should assume two-gyro operations for Cycles 17 and 18. This will ensure their programs will continue to be implemented in the event that SM4 is delayed substantially. Proposers should note that WFPC2 will not be available following SM4, and proposals using that instrument in Cycles 17 and 18 will not be accepted. In addition, NICMOS operations after SM4 may need to be curtailed due to spacecraft power considerations. While WFC3 observations cannot be proposed now, we encourage proposers of multi-year NICMOS programs to consider whether future portions of their programs could be carried out with WFC3, if necessary. Updates on the planned usage of NICMOS post-SM4 will be provided via the Cycle 16 Announcement Web Page.

The following features also deserve special mention, but have not changed since the last cycle:

• Starting in Cycle 12, a java-based software tool, APT (the Astronomer's Proposal Tool; see Section 1.4.6) is the interface for all Phase I and Phase II proposal submissions for HST. Please refer to Chapter 7, Chapter 8 and Chapter 9 for a description of how to prepare and submit your Cycle 16 Phase I proposal using APT. The Phase I LaTeX templates that have been in use for many years are no longer accepted.
• The instruments offered for observations in Cycle 16 are: the Advanced Camera for Surveys (ACS); the Fine Guidance Sensor (FGS); the Near Infrared Camera and Multi-Object Spectrometer (NICMOS); and the Wide Field and Planetary Camera 2 (WFPC2). ACS was installed on HST in March 2002 during servicing mission SM3B. NICMOS resumed operations after the installation of a cryo-cooling system. All of these instruments are working nominally at the time of writing this document (October 2006). Proposers should consult the Cycle 16 Announcement Web Page for up-to-date information on the status of all HST instrumentation.
• STScI experience with scheduling Large and Treasury Programs in Cycles 11 through 15 has shown that some programs can introduce substantial difficulties in developing an effective and efficient long-range observing schedule. Proposers submitting Large and Treasury Programs are asked to include additional technical details (e.g., orient constraints, tiling strategy for large mosaic programs and time constraints) in the "Description of the Observations" section (see Section 9.2) to provide information on the scheduling aspects of their program.
• In addition to the proposal categories that have existed for many cycles, STScI continues to solicit proposals in the categories of 'Treasury Proposals' (see Section 3.2.6), 'Theory Proposals' (see Section 3.4.4) and 'Legacy AR Proposals' (see Section 3.4.2), all of which were started successfully in Cycle 11. Also, it remains possible to request observing time on Chandra (see Section 3.5), NOAO telescopes (see Section 3.6) and Spitzer (see Section 3.7) in combination with requests for HST observations.