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Dr. Lekrone,

Here is the summary of the impact of ACS suspend that you requested.
The loss of ACS operations for the period spanning Monday June 19
through Sunday evening July 1 has impacted 154 prime GO ACS orbits
and 9 ACS SNAP observations. For the following week, July 3-9, the
data is less absolute since that schedule had (has) not been
completed. However, we do know that there are only at most 30
non-ACS orbits available for that week. Given the fact that we
nominally schedule 70-72 orbits total per week on average, that
would indicate that there was opportunity for a minimum of 40 ACS
orbits on that week, plus some number of ACS SNAPS. This implies
then that if the ACS is fully recovered by July 10, the total impact
of the ACS suspend will be at most ~200 prime GO orbits (154 + ~40).
The impact to these observations is shown in the individual program
summaries appended below.

Note also that in order to maximize the overall observatory efficiency
after the anomaly event, we intercepted the June 19 SMS and reworked
the June 26 SMS to substitute available non-ACS observations for the
impacted ACS activities. As the following summary shows, there is only
a limited number of non-ACS observations available to replace the
lost ACS opportunities. Where possible, we also scheduled additional
non-ACS SNAP visits.

prime prime prime
ACS non-ACS GO SNAP
orbits orbits net visits
Schedule dropped: added: loss: added:
June 19-25: 59 38 21 15
June 26-Jul 2: 95 52 43 38

Finally, as indicated in the individual proposal summaries, we will be
able to replan most if not all of the impacted ACS observations later
in 2006. The net impact is the delayed completion of the affected
Cycle 14 observations by 3 to 6 months. In addition, as many as 200
Cycle 15 orbits will need to be be delayed in order to make room for
the displaced ACS activities. Some of these observations will need
to be delayed well into Cycle 16, but the actual effect on the Cycle
15 observing program is not yet known since its observing plan is
still being reworked in response to the suspend event.

Please feel free to call or reply for clarification or with additional
questions.

--Bill

The following represent the majority of the prime GO science programs
affected by the suspend:

prop PI orbits Title/impacted orbits/replan options
10496 Perlmutter 5 "Decelerating and Dustfree: Efficient Dark
Energy Studies with Supernovae and Clusters"
This is a Cycle 14 Large/Target of
Opportunity program. These orbits were part
of the search for or follow-up on Type Ia
supernovae.

Impact: Since the current opportunity is past, the impacted orbits
will be given back to the science team to use as they deem necessary
for future search and follow-up opportunities.

10503 Da Casta 15 "The Star Formation Histories of Early Type
Dwarf Galaxies in Low Density
Environments: Clues from the Sculptor Group"

Impact: These are the last observations to be executed for this program.
They have scheduling opportunities for ~ the next 6 weeks.

10521 Surace 50 "ACS Imaging of a Unique Spitzer Field:
Morphology of mid-IR Variable Sources"
This program aims to accomplish a
"...large-area mapping mosaic covering a
roughly circular area 15 arcminutes" over
25 grid points.

Impact: These orbits are tentatively replanned for November-December 2006.

10563 Dye 10 "Accurate dark-matter mass profiles in 3
elliptical galaxies as a test of CDM"

Impact: These observations have been replanned for September 2006.

10632 Stiavelli 68 "Searching for galaxies at z>6.5 in the Hubble
Ultra Deep Field" This is a Cycle 14 Large
program. This program obtains "deep ACS
(F606W, F775W, F850LP) imaging in the
area of the original Hubble Ultra Deep
Field NICMOS parallel fields and - through
simultaneous parallel observations - deep NICMOS
(F110W, F160W) imaging of the ACS UDF area."

Impact: Observations can be replanned throughout the summer into
fall 2006, however, this will require removing the spacecraft
orientation restriction. This means that the parallel deep NICMOS
imaging will not cover the ACS UDF field. The PI recommended this
course of action to ensure that the primary science goals are met.