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From: JR Tate <email@example.com>
Subject: Clementine II Science Meeting
Date sent: Tue, 15 Apr 97 22:20:23 GMT
Here are some preliminary notes on the Clementine II Science meeting that I
recently attended in the USA. They are far from complete, but should give you
a flavour for the sort of things that were discussed.
Notes on the Clementine II Science Meeting
Held at HQ US Air Force Space Command, Peterson AFB, Colorado Springs
27th - 28th March 1997
Colonel SP Worden, the Deputy Director Requirements, US Air Force Space
Command, introduced the meeting, and gave an overview of the Clementine
Clementine I was designed to demonstrate military technology, and, at the
same time managed to do some "neat science". It was, however, a shame that
the asteroid fly-by element of the mission failed.
There is high interest in Congress in the programme. $45 million has been
allocated, along with funds from the US Air Force budget, for a follow-on
mission (Clementine II). The White House has directed that this mission is to
be a collaborative effort with NASA. This cold result in a shuttle launch,
allowing a larger payload.
The USAF has recommended that Clementine II should be a deep space mission,
with a launch date in late 1999 or early 2000, and should include interaction
with an Earth crossing asteroid. NASA will lead the science aspects of the
mission, while AFSPC will be the overall mission leaders.
Hopefully Clementines I and II are the first of a series of joint missions.
The Clementine II mission will be totally unclassified, and there are
possibilities for international co-operation.
There is, as yet, no DoD approval for an asteroid rendezvous, but Congress
has expressed its interest in asteroid research. A decision of the mission
profile will be announced in August 1997. There are three possibilities:
a. Earth Orbit mission
b. Full mission, including at least one asteroid encounter.
c. A hybrid mission.
A treaty compliance meeting has already taken place, and there seem to be no
problems with any of the planned mission profiles.
Planetary Defence is not yet a formal DoD mission, but there is a study
underway at the moment, and it seems likely that it will become so in the
An interagency agreement is expected to say the necessary surveillance
technology and assets exist, and that the planned asteroid science to be done
by Clementine II is necessary.
The NASA director, Dan Goldin, regards Clementine II as a very exciting
mission, and this feeling is echoed by the NASA senior management.
NASA welcomes involvement, as long as:
a. NASA is to lead on science matters.
b. The science cost is affordable.
c. All treaty commitments are observed.
Dr Eugene Shoemaker will lead the science definition team, to report to NASA
in September 1997. The final NASA decision will be published in the same
A NASA Science Announcement of Opportunity (AO) will be published soon
Foreign institutions may apply, but will require governmental support to be
JPL will provide engineering and programme support.
NASA has a number of related missions in train:
Fly-by of Mathilde in Jun 97
Rendezvous with Eros in Jan 99
Launch in Feb 99
Sample and return mission to Comet Wild 2 in 2004
Deep Space 1 (a New Millennium Mission)
Launch Jul 98
Fly-by of asteroid McAuliffe in Jan 99
Fly-by of a DS1 will fly by comet West-Kohoutek-Ikemura and the planet Mars
As an aside, it was stated that the official view is that an asteroid or
comet passing within 7.5 x 106 km of the Earth is regarded as a Hazardous
USAF PL/SX - DAVID BARNHART
Clementine II is primarily a military mission, but there is, and will be a
synergistic relationship with NASA.
Instrumentation will be designed for dual military/science roles.
A microsatellite is defined as a 3 axis stabilised device, with a "wet" mass
of between 2 and 20 kg.
There was a funding shortfall in FY 96/97 resulting in contingency planning
for reduced mission profiles. The current options are:
a. Earth orbit
b. Asteroid mission
c. Hybrid mission.
The final choice will depend on funding decisions made in September 1997.
A Titan II launch has been "booked" for Clementine II, but a free Shuttle
launch would be a much better option, assuming that "HAZMAT" safety problems
can be resolved.
DR. EUGENE SHOEMAKER
The Science Definition Team will have to look at two things:
a. What science can be achieved with the Air Force mission hardware?
b. What extra instrumentation can be fitted to the spacecraft?
LLNL - DR. ARNO LEDEBUHR
The Clementine II bus will go for a 50-100 km fly-by of the target asteroid.
There will be a suite of Integrated Mission Sensors.
Bus range at probe impact will be 100-300 km, before closest approach.
Probes will be released about 3 hours before impact.
Bus navigation system will be switched off when the target asteroid fills the
CCD field of view.
The asteroid capable probes will be 30"-40" long, weighing 19.6 kg.
There is, therefore, not much opportunity to fit additional science packages
on the impact probes.
Optical sensors have been chosen, as they are not anti-ICBM capable, and the
probes will only be capable of low relative velocities. These measures are
required for treaty compliance.
The Clementine I sensor suite weighed 7.5 kg and consisted of:
Near IR camera
Long wave IR camera
The Clementine II package will include a telescope with five channels:
High resolution visible
Medium resolution near IR
Medium resolution Long Wave IR
Profiling LIDAR (ranger)
The mothership will have 8 Gb of memory on board.
The optimal distance for asteroid targets is 0.2 AU to give useable radar
The nominal Clementine II mission will visit two asteroids.
Best fit for the mission so far would be:
1986 JK - a C-type asteroid, possibly a dormant or extinct comet (dynamic and
spectral evidence available).
c. 1 km diameter in an orbit typical of Jupiter family comets.
4179 Toutatis - S-type (from the inner asteroid belt and Earth crossing).
Possibly the best known ECA and the location of its centre of mass is known
to within 10 cm at any time.
1.92 x 2.40 x 4.60 km in size.
Launch opportunities for missions to both of these are 4 June 1999 and 10
Dr. Eugene Shoemaker
Dr Shoemaker described what he called "the ECA zoo".
Many of the asteroids that we see now are fragments of the cores, mantle and
crust of larger, differentiated parent bodies. In addition there are extinct
comets from both the Oort cloud and the Kuiper belt.
We need data on asteroid compositions, sizes and spin states.
Questions on Structure
Are they structurally coherent?
Do they have fractures or faults?
Are they debris piles?
If so, what is the size distribution of fragments?
Were the primitive parent bodies homogenous or heterogeneous?
If the parent bodies were differentiated, compositional or volcanic
Craters and regolith indicate the age of a body and its evolution.
Are they homogenous or heterogeneous?
Are they single or multiple bodies?
What is their surface structure?
Do they have vents or fissures?
Will the probe impact "turn on" cometary activity?
There followed a discussion on impact science led by Dr Greg Canavan who
pointed out that the vapour effect indicates compressional strength of the
target, while rubblisation indicates tensile strength.
Dr Tom Ahrens explained that the cratering of small asteroids is controlled
by their structural strength. For larger bodies gravity is the controlling
influence. The threshold between the two is at an approximate diameter of 150
metres. He added that structural strength decreases with decreasing size as
fault configurations become more critical.
The fact that shocked gasses from an impact fluoresce may be useful in
determining compositions. However, the spectra obtained from the gas plume
from the impact would be contaminated by vaporised material from the
POTENTIAL SECONDARY MISSION OBJECTIVES
Dust Studies - Dr. Tom Economou
Planetary / Satellites
Man made space debris
Various dust detectors were described.
Survey for Asteroids - Dr. Duncan Steel
Dr Steel discussed the advantages of searching for Earth crossing asteroids
from the spacecraft, but noted that the detection rates would probably be
He pointed out that meteoroid orbits do not resemble those of comets, but
look like those of the Aten family. There appear to be two main source
directions, anti-helion and helion.
He warned all present of the likelihood of a major meteor storm on 17th
November 1999, the Leonids. This storm recurs at 33 to 34 year intervals, and
is expected to be particularly heavy in 1999. This event could pose a
considerable threat to satellites or other assets in Earth orbit.
Search for Microlensing Effects
It was suggested that the Clementine II spacecraft would make a good platform
for observing microlensing effects caused by Dark Matter. This would be
achieved by measuring parallax effects. Similar research has already
indicated the presence of MACHOs in the galactic halo, and that the Milky
Way is a barred spiral galaxy.
OPTIONS FOR AN EXTENDED MISSION
Assuming that the primary mission objectives are achieved there may be
potential for extending the spacecraft mission to achieve further scientific
goals. A number of possibilities were discussed.
Return to the Moon
The spacecraft could be inserted into a low polar orbit around the moon. It
would then use its LIDAR to accurately determine the topographic
configuration of the lunar surface.
One major task would be the production of an accurate radar map of the
possible ice deposits at the lunar pole discovered by Clementine I.
Confirmation of the existance of substantial quantities of ice could have a
profound effect on the future exploration of the solar system. Ice would be
detected by using the Coherent Backscatter Opposition Effect, probably using
the spacecrafts main communication dish as a radar antenna.
Deep Space Profiles
The possibility that the spacecraft could be configured to travel to Mars, or
the inner asteroid belt were discussed. It was agreed that these profiles
were possible, and would be considered further.
Ground Based NEO Surveys
There then followed a briefing on Ground Based NEO Surveys, including:
European Activity - Richard Tremayne-Smith (BNSC)
It was stated that the European position is that mitigation of potential
impacts is not an issue until Clementine II and Rosetta type missions have
ESA is undertaking a study of the NEO threat.
The Spaceguard Foundation - Dr. Duncan Steel
The Spaceguard Foundation currently has 53 members, with 13 pending
There are associate organisations in Japan and the UK, with organisations in
Germany, France and Finland pending.
ESA has allocated $100,000 to the Foundation to help establish a central node
for NEO data.
If you have any questions or comments, please get in touch.
CCCMENU CCC for 1997