[meteorite-list] EPOXI Mission Status Report - October 20, 2011

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 3 Nov 2011 11:07:40 -0700 (PDT)
Message-ID: <201111031807.pA3I7eGG009836_at_zagami.jpl.nasa.gov>

http://epoxi.umd.edu/1mission/status.shtml

EPOXI Mission Status Report
Michael A'Hearn
October 20, 2011

The spacecraft went through a cool-down period at the end of
September to optimize the capabilities of the near-IR spectrometer and
to carry out a Trajectory Correction Maneuver (TCM). This maneuver
changed our target point based on our improved knowledge of the position
of the comet relative to the spacecraft. We think that the new target
point will be within 100-200 km of the desired flyby point (which is 700
km from the nucleus). We expect our next and final TCM to be on October
27. We have a contingency plan for a TCM on November 2 in case the
previous TCM does not perform as expected.

We have been receiving Hartley 2 data from a variety of other spacecraft
and collaborators. The WISE mission released data acquired in May.
Those data will be useful in understanding the onset of activity by the comet
as it approaches the sun in its orbit. Weaver et al. released
Hubble Space Telescope images acquired on September 25. The HST images
are particularly valuable because they allowed us to confirm that the
cometary nucleus is separable from the coma. Eventually, we will be able
to separate the nucleus from the coma within our own data. For now, HST
has a huge advantage over our own cameras in this respect due to the
much larger aperture of HST coupled with the fact that Earth and HST
were much closer to the comet than was our spacecraft. These data are
consistent with earlier determinations of the size of the nucleus.

We have also been receiving widespread reports of jets in the coma of
the comet. The first such report was from Matthew Knight and colleagues
<http://www.lowell.edu/rsch/content/comets/hartley2/hartley2.html> at
Lowell Observatory who found jets in the gas (the unstable radical CN)
but not in the dust during an August observing run . Since then, we have
had more recent reports of jets from both professional and amateur
observers.

Since the Deep Impact spacecraft has its cameras dedicated to monitoring
Hartley 2 during this phase of the mission, we now have an advantage
over other observatories and telescopes because we have nearly
continuous coverage (16 out of every 24 hours). We too see fluctuations
and jet-like structures in our data that are presumed to be due to
variations in the release of dust and gas as the nucleus rotates. More
excitingly, we have discovered a new cometary phenomenon!
In September, outgassing from CN, as
detected by the MRI, increased slowly by a factor of 5 and then slowly
decreased while the dust showed no dramatic change. This activity took
place over the course of 16 days. We are unaware of any other instances
of this type of activity in any other comets and it is very different
from the dust outbursts observed with the same instrument at Tempel 1.
(Reported in CBET 2512
<http://www.cbat.eps.harvard.edu/cbet/RecentCBETs.html>, which requires
a subscription to view.)
Received on Thu 03 Nov 2011 02:07:40 PM PDT