[meteorite-list] Deep Impact Mission Update - May 2005

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun May 22 22:40:48 2005
Message-ID: <200505230240.j4N2eCh12222_at_zagami.jpl.nasa.gov>

http://deepimpact.jpl.nasa.gov/mission/update-200505.html

Deep Impact Mission Update - May 2005

Mission Update - May 2005
With information from Dave Spencer, Dennis Wellnitz, Lucy McFadden, and
Don Hampton

May 5 - Deep Impact TCM-3A Performance

Deep Impact performed TCM-3A on Thursday at 1900 UTC. The 5.05 m/s
maneuver was performed flawlessly, with an execution error of less than
0.2%. Early orbit determination indicates that we are within 25 km of
our B-plane target, and are within 1 sec of our desired time of flight.

This TCM was biased early in time of flight by 10 minutes, to ensure
that TCM-3B (planned 11 days before encounter) will be in a direction
that is favorable for spacecraft power, thermal, and telecom
considerations. Following TCM-3B, we should be on a near impact
trajectory with comet Tempel-1. Timing of the impact is being adjusted
to provide good viewing opportunities by the Hubble Space Telescope and
the Earth-based Mauna Kea observatory.

--Dave Spencer

------------------------------------------------------------------------

Dennis Wellnitz

May 10 - May Science Calibration

On Tuesday, May 10, we successfully ran the first day of the May Science
Calibration. All targets, including those viewed by the ITS on the
Impactor spacecraft, were positioned within the various fields of view
with exposures at the desired levels.

We obtained a calibration spectrum of the star Beta Hyi. We also took IR
data on the globular cluster 47 Tuc, and took context images with the
MRI through the clear filter.

We obtained good calibration data through all filters with the HRI-VIS
and MRI-VIS on the stars i Car, Beta Hyi, Canopus, and Achernar. We also
obtained good calibration data on these same stars plus HD 60753 with
the ITS. This was accomplished with much smaller fields of view (128x128
pixels for MRI-VIS and ITS, and 256x256 for HRI-VIS) than were used in
the April Science calibration. The HRI-VIS star images provide multiple
well-exposed measurements of the Point Spread Function through each
filter, with varying pixel registration.

Over-exposed images of Canopus in all quadrants of the HRI-VIS, MRI-VIS
and ITS provide electronic cross-talk corrections. We also obtained
darks in MRI-VIS and ITS.

The crowning achievement of the first day of calibration was an ITS
mosaic of the open cluster NGC 3114.

We plan to continue with the second day of the May Science Calibration
on May 11.

--Dennis Wellnitz

------------------------------------------------------------------------

May 17 - Other Science Team Activities

Just after TCM-3A on May 5, the mission entered its approach phase which
includes the time period from 60 days to 5 days before impact. We are
observing the comet repeatedly in this phase to detect the nucleus and
to refine knowledge of the positions of both the spacecraft and the
comet. We can see the comet in our imagers now and are monitoring its
brightness changes with time. Observations are limited to about 15
minutes every 4 hours because of the position of the Sun with respect to
the comet. We can't allow the sun to shine on the instruments.

Don Hampton, one of our instrument engineers, reports the following:

"As part of the May science calibration we took an MRI image (actually
there are 6) of 47 Tucanae (also NGC 104), which is a bright globular
cluster near the Small Magellanic Cloud. The MRI images were to help
determine where we were pointed during an IR scan of the cluster.
However, the cluster image is very pretty, so I fixed one up to send
out. This is a logarithmic stretch so that all the little dim stars are
visible as well as the brightest stars."

While the spacecraft is taking data, the science and mission operations
teams are reviewing the sequence of observations and commands to execute
them for the Encounter phase, beginning 5 days before impact. The
process of designing, reviewing, testing and uploading spacecraft
commands that collect the data to complete our experiment is very
carefully carried out by teams representing all parts of the spacecraft.
(See our Sequence Symphony <../science/observations-sequence.html> article.)

The members of the project definitely feel the speed at which the comet
is moving through the Solar System. Things are happening quickly and we
feel like we're moving at 10 km/s (23,000 mph)!

--Lucy McFadden
Received on Sun 22 May 2005 10:40:12 PM PDT