Here are some links with recent information on BepiColumbo:

Europe Eyes Messenger of the Gods
http://www.chron.com/content/interactive/space/astronomy/news/2000/sol
arsys/20001013.html
"The Mercury mission will comprise two orbiters and a lander, Roger
Bonnet, director of ESA's science program, told journalists."

"One of the orbiters will loop over the poles at a height of 400 to
1,500 kilometers (250 miles to 950 miles), carrying two cameras and
spectrometers to map the planet's surface and monitoring its gravity
and rotation."

"The other will observe Mercury's magnetic field and its interaction
with the solar wind, the blast of ionised particles that radiate from
the nearby Sun."

"The lander will be a fixed probe that will be sent down to a
relatively mild polar area, carrying a camera, seismometers and
instruments to measure the temperature and hardness of Mercury's
surface."

"The orbiters will be designed to operate for a year, while the lander
will operate for "at least" a week, according to the mission's
specification."

The following is an excerpt from a post by John Rehling to the ISSDG
mailing list (one of the two I run):

"Two orbiters! I trust that, as someone here had already hypothesized,
that the primary imaging orbiter will have a periapsis complementary
in latitude to MESSENGER. Then the magnetic field orbiter ought to
have an inclination complementary to MESSENGER's. If both are
operational at the same time, the quality of the science regarding
Mercury's magentic field and its interaction with the Sun as Mercury
varies considerably in its distance from the Sun could be of essential
interest, much like the simultaneous Cassini-Galileo observations. In
fact, this could churn out even more interesting results, as they'd be
over a much longer time, with much more variety in the data due to the
rapidly-changing spacecraft locations with respect to Mercury, and
that of Mercury with respect to the Sun. This is the best reason yet
for flying both missions.

I'm not sure I get the lander's mission. Ground truth imaging will be
interesting to an extent (does anyone expect it not to look like the
Moon?). Seismology could be a top-notch mission goal, but only if the
sensitivity of the instruments is sufficient. Also, a short lifetime
for the lander (a week) minimize the chances of seeing seismic
events.
Is there still still trace volcanism on Mercury? Is there still modest
crustal compression? Note that not only Mercurian seismology but also
the influx of impactors in that part of space is of interest. But I
don't see much point to the temperature and material strength
observations. Temperature can be monitored from orbit, or even from
Earth. Local thermal inertia (won't even survive one dawn or dusk) and
structural properties -- I don't see much point.

Surface composition would be of great interest. Particularly, as (over
timel won't happen in this mission), the different terrains on Mercury
were dated. Mercury appears to be a touch younger than the Moon;
verifying these dates would tell us a lot about the planet's thermal
history as well as impactor populations in the first billion years of
the solar system. But BC won't get a chance to do this.

Overall, I see more point to the mission now than I did before. Also,
a lander would give ESA their first striking "first" in planetary
exploration (on a mission that is ESA all the way; Mars Express
results pending)."

The following is a reply to this excerpt by Bruce Moomaw:

"Where have you been, Mr. Rehling, over all these past months of my
interminable fight with Robert Clements over the value of Bepi
Colombo?
We've both been pointing out from the start that there were two
orbiters on
this thing: a big mapping orbiter (by far the biggest and most
expensive
part of the project) which would be put into a much lower-altitude
elliptical orbit than Messenger, and a much smaller spin-stabilized
magnetospheric orbiter which would be put into a highly elliptical
orbit.
We've also agreed with the ESA that it would nice if the latter could
make
simultaneous magnetospheric measurements with Messenger (although,
according
to the current schedule, Messenger will have completed its one-year
primary
mission two years before B.C. even gets to Mercury). The squabble has
been
over whether that big mapping orbiter is worth its very high cost,
even
given that it will provide higher-resolution coverage of Mercury's
southern
hemisphere than Messenger.

I also maintain that ESA isn't even playing to its primary scientific
strength in this mission -- namely, that lander. Clements says that
"about
90%" of the scientific value of B.C. lies in its lander; I don't go
quite
that far, but it's certainly by far the biggest thing B.C. will do
that
Messenger won't. But, as you say, it won't even work more than a week
or
so, which means that its seismic data (one of the most important
things it
could do) will be so brief as to be almost worthless. Now, if B.C.
consisted of two or three small but long-lived landers focusing on
seismic,
surface-composition and maybe heat-flow data (imaging, as you say, is
much
less important), plus a small cheap data-relay orbiter that could also
make
some high-priority scientific measurements, it really would make
sense --
and it would also make sense as a mission by itself even if Messenger
failed. But ESA is apparently pigheaded in their determination to
flush at
least $200 million of their hard-earned dollars down the toilet (the
cost of
the current B.C. mission is 466 million U.S. dollars). There's
nothing I
can do about that. The only remotely sensible thing they've done,
according
to the official announcement, is collaborate with Japan on this
mission
(although I have no details)."

Here is a excerpt from a post on ISSDG by Robert Clements:
"The lander's basically an upgraded version of the Japanese Lunar-B
impactors (or the failed DS2s)... i'm not sure whether they will be
ESA
designs or ISAS/ESA coops (the Japanese have definitely folded their
own
Mercury orbiter plans into BepiColombo). My guess is that the the
nominal
mission is rather like Sojourner's; & very nominal indeed: if the
impactors are still doing surface science after a week, they probably
last quite a bit longer."
"As with all impactors, the goal is to make subsurface sampling
measurements; & also demonstrating that this theoretical technology
can
actually be made to work (something the Japanese have struggled with &
NASA spectacularly failed at)... everything else is scientific cream.
I
like the idea of it being able to do surface imaging, though...."

Jason Perry
volcanopele@...
Moderator of the Outer Planets Mailing List (subscribe at
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Webmaster of the Io Home Page (
http://members.fortunecity.com/volcanopele/ )