Conference 7.286::space

792.0. "ROSETTA Comet Probe (ESA)" by VERGA::KLAES (All the Universe, or nothing!) Thu Apr 09 1992 12:06

Article: 42668
From: [email protected] (Josh 'K' Hopkins)
Newsgroups: sci.space
Subject: Rosetta summary
Date: 8 Apr 92 22:37:41 GMT
Sender: [email protected] (News)
Organization: University of Illinois at Urbana
 
	A few people mailed me privately on topic relating to the
comet discussion that's been going on.  Since they didn't know about
Rosetta, and many other people don't seem to, I though someone should
post a summary. 
 
	Rosetta (as in the stone) is one of the 4 major missions
planned in ESA's Horizon 2000 program.  It is designed to return comet
samples to Earth for study.  They would need substatial help from the
international community, and are planning on major help from NASA
(does this sound familiar? :) 
 
	The mission is to return core samples (10kg), volatile samples
(0.1kg) and nonvolatile surface samples (1-5kg) for study of
compostion, structure etc.  Naturally, this means a fairly complex
return vehicle that has to maintain low temps during reentry. 

	In situ science includes high precision orbit determination
and study of emission patterns, analysis of coma and nucleus during
entry phase, and studies related to sample aquisition.  The baseline
mission does not include much in the way of surface science, since the
main mission is to return the samples, but they are considering a
surface package that would remain on the comet long term. 

	Several comets with perihelion under 1.5 AU and aphelion under
6 AU are possible targets. I won't include names or dates since thay
are likely to be out of date. 

	The vehicle consists of three parts.  A Mariner Mk II type
carier provided by NASA, a lander which has the sampler, major payload
equipment and the landing/anchoring system (this stays on the comet)
and finally, the aerocapsule, which is attached to the carier.  Launch
is planned for a Titan IV Centaur, with one Earth swing by and about a
four year flight. 

	Target aquisition would take place a few million kilometers
out, and R would approach the sunlit side over a period of 25 days. 
At this point, the distance is about 100,000 km, folowed by another 25
day period during which R slowly approaches, starting observations
5000km out.  This gives it about 5-10 days to observe as the comet
rotates under it.  At 100 km out, R stops and ground control decides
on a landing site.  After about 15 days, during which camera
resolution is about 1m, R begins hyperbolic flybys over potential
sites during good lighting conditions.  Minimum altitude is 20 km. 
When the landing site is determined, a penatrator with a radio beacon
is impacted in the target zone, and R eventaully lands nearby (within
20 m)  If microwave instruments indicate than the surface is too rough
or that sampling won't be possible, R aborts to a higher altitude and
waits for Earth input. 

	Landing gear includes harpoons under tension to keep the
spacraft from flying off when torque is applied to samplers.  Two
surface samplers, 50cm x 10cm diameter will be filled with material
within a 1m radius.  Two to six core samples (dug in the same place to
increase depth) will be be taken over a period of ten days.  If
landing or sampling is impossible, a backup system is included.  R
hovers above the comet, and a spin stabilized harpoon collects a sample. 

	After sampling is complete, the carier and return capsule take
off at 10 m/s and move away from the comet for 10 to 20 days.  Then
the Earth return procedure is implemented.  3 years later, the craft
returns on a trajectory that misses Eath by 1000 km.  24 hours before
reentry, the RTG is ejected. The craft then maneuvers onto a re-entry
trajectory. 2 hours before reentry, the carrier seperates and burns
out of the reentry trajectory, leavin the return vehicle to enter the
atmosphere.  Deccelleration must be below 50-100 g and thermal flux
must be kept very low.  At 25 Km altitude, the parachutes deploy, and
the vehicle lands within 20km of its target destination. 
 
		Hope this helps,

			Josh Hopkins
 
    Source, ESA Bulletin, August 1989.

From:	US1RMC::"[email protected]" "ESAPRESS list" 12-NOV-1993 00:18:19.34
To:	[email protected]
CC:	
Subj:	ESA confirms ROSETTA and FIRST in its long-term science programme 
        [ESA  Release 43-93]

Press Release Nr.43-93
Paris, 8 November 1993

ESA confirms ROSETTA and FIRST in its long-term science programme

At its 68th meeting on 4/5 November 1993, ESA's Science
Programme Committee endorsed the recommendation of the
Space Science Advisory Committee to implement ROSETTA,
a comet rendezvous mission, as the third cornerstone and
FIRST (the Far Infrared Space Telescope) as the fourth
cornerstone of the Horizon 2000 programme. The launch dates
will be 2003 and 2006, respectively. However, FIRST would
return its scientific data earlier than ROSETTA, as the travel
time to the comet is rather long.

ROSETTA was originally conceived as a comet-nucleus
sample-return mission that should have brought back cometary
material to Earth to be able to study it with the most advanced
laboratory analysis techniques available.

The original mission could not be implemented as it was too
ambitious and too complex. Therefore in 1992 the concept had
to be revised. The mission was reconsidered as being
performed by ESA alone on the basis of European technology
and the Ariane 5 launch capability. However, the opportunity
for other agencies to join and augment the scientific return
was left open, and international partners have already
indicated to ESA their interest to join.

The new baseline mission is a rendezvous with a comet and
at least one (most probably two) flybys of asteroids. After
gravity-assist manoeuvres at the Earth and Mars or Venus
to acquire the necessary energy to reach the comet at its
aphelion (the part of the orbit farthest from the Sun), the
spacecraft will stay with the comet along its trajectory into the
inner solar system through perihelion (the orbital point nearest
to the Sun) to study the material that constitutes the comet,
and the cometary processes that evolve with the decreasing
distance from the Sun. A Surface Science Station will be
deployed onto the comets' nucleus surface to provide the
means for in-situ studies of the nucleus.

The mission retains as far as possible the objectives of the
original comet-nucleus sample-return mission and concentrates
on the in-situ investigations of cometary matter and the
structure of the nucleus. "As we cannot bring the cometary
material into our terrestrial laboratories, we will take our
laboratories to the comet" said Dr. Roger Bonnet, ESA
Director of Science. Potential target comets are Schwassmann-
Wachmann 3, Wirtanen, Finlay and Brooks 2 for a launch in
the time interval 2002-2004.

"Both teams for ROSETTA and FIRST" added Dr. Bonnet,
"defined excellent missions with exciting prospects for the
science to be achieved. For programmatic reasons ROSETTA
will be implemented as Cornerstone 3, following Cluster and
SOHO and XMM".

"However", he continued, "the work on FIRST will proceed at
a very high level to further develop the critical technologies,
like for instance the 3 m telescope mirror, the coolers and the
detectors. The major elements of the  Horizon 2000 science
programme are now under way and we will start the process
to define the 'post-Horizon 2000' programme".