Transcript rosetta

Ratio of KE to binding energy
mass ratio
newton third law force
Mass = 3 x 10^12 kg
Density = 0.1 -0.4 !!!
Dust coma August 1
Past Missions to Comets (2)
• Deep Impact – launched a 350 kg copper
impactor into the nucleus of comet
9P/Tempel 1, in July, 2005.
– A 100 m x 25 m crater was created.
• Visible and infrared spectrometers on the
parent craft looked for the composition of
the nucleus.
– 250,000 kg of water vapor were detected.
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Current Missions to Comets
• Stardust – sampled the coma of P Wild 2
from a distance of 236 km above the
nucleus.
• Returned comet particles back to the earth
for microscopic examination and chemical
testing.
You can help with the microscopic work by
signing up at the following website.
http://stardust.jpl.nasa.gov/home/index.html
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Cometary Orbits &
Comet Reservoirs
•
Members of the solar system in
very eccentric orbits
- Oort Cloud comet
- long-periodic comet
- short-periodic comet
 no interstellar comet
•
Comet reservoirs
- Oort Cloud
- Kuiper Belt (+Centaurs)
with “graveyards” for
- Jupiter family comets
- dormant comets
- main belt comets ?
Comets & Earth Ocean Water
•
•
Earth after formation: hot, hence
no water on Earth
Clean-up of formation disk
produced
bombardment
(most likely in 2 phases)
 import of water on terrestrial
surface
Problem: D/H ratio of ocean
water differs from
(barely
known) D/H ratio of comets
 way-around: mixing of 2 or
more sources with
different
D/H ratio,
cometary source
would have contributed
about 30%
early bombardment
late bombardment
(comets?)
Organics in Comets
•
Comets contain organic
compounds both in volatile
ices (simple
organics) and
solid dust (CHON, most
likely more complex
organics)
 long-term storage facility
•
CI chondrite meteorites are
most likely
related to
comets
2 CI chondrites
had amino
acids with
preference for
left-handed enantiomer
 contribution to life formation
on Earth (if cometary
material
can reach Earth
surface reasonably intact)
The Latest Coup: Deep Impact Live Impact & Cratering Experiment
•
NASA mission to 9P/Tempel 1
- impact: 4 July 2005, 05:52UT
- impactor: 360kg
– speed: 10 km/s
– vis. camera
– fly-by S/C: vis. cameras
& IR spectrometer
– impact site visibility:
14min
Deep Impact: Learning by Doing
• impact: shot in the blind
• shape of ejecta cloud indicates
low strength dominated
impact regime
• DI impact crater not found
 cratering science suffers
(now to be imaged by
STARDUST in 2011)
• surface: many natural craters
 occurence frequency
consistent with expected
cratering rate of inactive
body
 but impact craters should not
survive cometary activity for
very long (erosion rate
~ 1 m/rev)
DI: The Expected & the Unexpected
• low bulk density 0.6 g/cm3
 Kuiper Belt objects are
heavier (Pluto: 2 g/cm3)
• low thermal conductivity
(100 W/K/m2/s1/2)
 very porous material
• comet: very weak (~300 Pa)
(weaker than powder snow)
 loosely bound, signature of
soft aggregation process
during formation, unclear
whether planetesimal or
impact formation
1km
The ROSETTA S/C
• ROSETTA Orbiter (ESA)
Dimensions:
Weight:
2.8 x 2.1 x 2.0 m
3000 kg
1600 kg fuel
165 kg experiments
Instrumente:
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- close sensing (~ telescopes)
- in-situ experiments (~ lab)
• PHILAE Lander (DLR/CNES/ASI)
Dimensions:
Weight:
0.7 x 0.7 x 0.9 m
100kg
15kg experiments
Instruments:
10
(telescope & lab & samples)
The Flight Schedule
Duration:
~ 10 years
 4x planet swing-bys
(Earth, Mars)
Cruise science:
2 x asteroids
Earth/Mars fly-bys
Science at comet:
> 1 ½ years in orbit
lander delivery
1 Launch Earth
02.03.2004
2 Swing-by 1/Earth
04.03.2005
3 Swing-by 2/Mars
25.02.2007
4 Swing-by 3/Earth
13.11.2007
5 Fly-by Steins
05.09.2008
6 Swing-by 4/Earth
13.11.2009
7 Fly-by Lutetia
10.07.2010
8 Rendez-vous comet
22.05.2014
9 Landing on comet
10.11.2014
OSIRIS - The
ROSETTA Eyes
© OSIRIS team
(close sensing)
2 cameras (wide & narrow
angle + stereo) for vis. + UV
wavelength region
Science: nucleus mapping
geology, activity
(backbone inst.)
Orion nebula
© DLR
© NASA
Resolution: 1 cm/pixel
 100 x better than any
existing comet image
Komet Wild2 mit STARDUST
Farbe
100x
1x
ROSINA – COSIMA
The Comet
Chemistry Labs
ROSETTA
(in-situ)
Science goal: original gas and
dust chemistry
cometary organics
Isotope ratio in comets
(ocean water from
comets?)
Instrument type: mass
spectrometers (lab exp.)
GIOTTO
Philae Lander Touchdown Dynamics
Revisited
L. Witte, S. Schröder, R. Roll, S. Ulamec, J. Biele, J. Block, T. van
Zoest
– Tests For The Upcoming Landing
Preparations –
10th International Planetary Probe Workshop, San Jose State University, June
2013
www.DLR.de • Chart 17 10th International Planetary Probe Workshop, San Jose State University, June 2013
Understanding Philae‘s Landing
Gear (1/2)
The landing gear consists of a foldable tripod and a central
damping mechanism. Its damping behavior can be simplified
as linear velocity dependent damping force.
www.DLR.de • Chart 18 10th International Planetary Probe Workshop, San Jose State University, June 2013
Understanding Philae‘s Landing
Gear (2/2)
A cardanic joint
between the tripod
and the central
damper unit allows the
This range was reduced to +/-3° by
LG to
adaptof the
to tiltthe
installation
limiter (late
change).
localdesign
terrain
(+/-30°).
Further elements (not shown):
• 2 anchoring harpoons,
• Active Descend System (ADS)
www.DLR.de • Chart 19 10th International Planetary Probe Workshop, San Jose State University, June 2013
Test Results: A Fully Asymmetric
T/D Condition
Example: Spec_2a , Vv=0.8m/s, Vh=0.2m/s,
r/p/y=17/0/90°, surface: wood
Cardan angle data
1 px = 1.1 meters
2.4 m per pixel
•
•
The computer processing power is about the same as that of a 1990s hand
calculator, however, the chips used were radiation hardened to survive
space conditions. Philae’s systems will be watching and making navigation
corrections throughout the descent. Nothing fancy, this is a simple and
straightforward execution with a modest control system on board.
Nevertheless, it has everything necessary to accomplish the soft landing on
a comet.
When studying the design, I first imagined that Philae would make a long
descent and the comet would make a full rotation. But rather, Rosetta will be
navigated to somewhere between 2 to 10 km above the comet surface then
release Philae. Because of the comet’s odd shape, the probes could be 4
km above the surface at one time and then just 2 km at another, due to the
rotation of the comet. The odd rotating shape means that the gravity field
effecting the descent will be constantly changing. One might compare the
effects of 67P’s gravity on Philae as similar to the motion of a well thrown
knuckleball (e.g., Wakefield, Wilhelm). Catchers resort to using a larger
catchers mitt and likewise, the landing zone (or ellipse) is 1 square
kilometer, sizable considering 67P’s dimensions are 3.5 × 4 km (2.2 × 2.5
miles).
ilae towards the comet, 2) Descent: the comet is rotating and its gravity is weirdly pulling on
• 3) Touchdown is when the CDMS will earn its
badge of honor. Upon touchdown, the control
system will fire the cold thrusters to push Philae
snugly onto the surface. At the same time, the
two harpoons will be fired to, hopefully, pierce
and latch onto the cometary surface. To further
prevent bounce or tipping, the dampener will
absorb energy of the touchdown. Philae is likely
to have some transverse velocity on touchdown
and this will translate into a torque and a tipping
action which the Harpoons and cold thrusters
will reckon with.