Minutes of Sept. 25, 2001, SIRTF Telecon, 1100 CDT

NEXT TELECON: OCTOBER 9, 1100 CDT.

Present: Babler, Churchwell, Clemens, Dickey, Kobulnicki, Marston,
Mathis, Meade, Stolovy, Watson, Whitney, Wolff, Wolfire

I. Observing strategy (Chip Kobulnicki, Christer Watson): we should
implement the strategy suggested by Marston some time ago: (a) forget
about eliminating faint asteroids, and correct for bright ones by
knowing their orbits; (b) step the arrays immediately by a small
portion of each frame (1/2 frame for double coverage, 1/3 for triple,
etc.)  The asteroid rejection is not vital, considering that most of
the time we will be rather far from the ecliptic. This strategy
results in fewer AORs and less slewing time (only 18 sec rather than
21?) compared with returning for the second observation after a few
hours.

A table had been distributed by email that gave the area surveyed as a
function of the number of pixels of overlap, ranging from 10 to 15
pixels. A general feeling of the telecon was that a 12 pixel overlap
should be tried as safe, but the matter will have to be evaluated in
flight. The same goes for the reliability and confusion limits.

Clemens: the MSX survey shows a source density about twice as large
for |l|\le.33 degrees as for |l|>33. Maybe a hybrid strategy will make
sense, with better coverage (3 passes?) for the |l|<33 part than the
outer (2 passes). The structure of the Galaxy needs good reliability,
and negative longitudes are just as important as positive because of
the Galactic bar asymmetry. Thus, symmetry around the GC should be
maintained.

Is the SSC happy with dumping the asteroid rejection? Apparently so;
they estimate that we will detect only (1 - 2)x10^4, amongst our
10^8 sources. Of course, the brighter asteroids are known and can be
flagged.

II. GTO overlaps (Ed): R. Gehrtz will want some 4 fields, possibly of
4x4 frames each, embargoed for one year. Berhard Brandl wants the W49,
NGC3603 regions embargoed (a reasonable response, given their
brightnesses). We will not get the relevant data from SSC, so there
will be gaps in our survey. We will make sure that only one of our
AORs will be affected. The GTOs can set priorities for the ordering of
their observations. However, the SSC may force the priority of embargoed
fields to be high, so that they will be observed in the early phases
of the mission. It may be possible that only the embargoed frames will
be missing from our data, rather than the entire AOR data.

II. John Carpenter, a 2MASS expert, is too busy to join our team, but
is willing to serve as "consultant", meaning that he will be willing
to extract 2MASS data for us. There is a useful Web page for 2MASS. Ed 
has also contacted Mike Skrutskie (UMass), who is involved with their
data.

III. Legacy Science Working Group (Ed): (a) There will surely be a
delay until Jan '03. If the delay slips to mid-Feb '03, than there
will be a slippage past mid-April. This will cause some problems
because of flat funding, but no one's job will evaporate. (b) We can
revisit our AORs in spring or early summer.

IV. Validation strategies: need launch date for precise decision 
regarding the best areas, probably at (launch + 2 months) or so.
We should consider 6 - 8 possible areas, about 1 deg square, involving
some "good" areas (little crowding) and some worst-case ones.

V. There should be a team minimeeting at the winter AAS, and probably
a full meeting in Madison in spring.

to Minutes index page