Transcript Planetary Emissivity Laboratory Facing the heat – Obtaining near infrared real emissivity spectra at Venus surface temperatures Jörn Helbert [email protected] J.

Planetary Emissivity Laboratory
Facing the heat –
Obtaining near infrared real emissivity
spectra at Venus surface temperatures
Jörn Helbert [email protected]
J. Helbert, A. „grill master“ Maturilli, N. Müller DLR
Planetary Emissivity Laboratory
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Otygen
Coronae
What actually Jord
are the red and Corona
blue materials on
the surface??
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Quetzalpetlatl
Corona
Boala
Corona
Jörn Helbert [email protected]
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Helbert, Müller et al.
GRL 2008
The answers can only come from laboratory work
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Jörn Helbert [email protected]
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Planetary Emissivity Laboratory
Now that we got data which might
indicate compositional differences, we
need to understand better how to
classify composition from only three
channels
In Berlin we have started to set up a
new Planetary Emissivity Lab which
will allow to measure the
wavelength range from 1-50μm for
samples at high temperature
(>700K)
This will cover the surface windows
observable by VIRTIS
However it will operate under
vacuum and will not be able to reach
more than (Earth) ambient pressure
Still it should be good to confirm –
or improve – this plot
Hashimoto and Sugita, 2003
Checklist for high temperature emissivity
measurements
1. Build and characterize a setup that
allows measurements with a good
signal to noise ratio for emissivity
measurements at 1 μm
For characterisation see Maturilli et al. 2008
Jörn Helbert [email protected]
2. Heat your sample to at least 400°C
2a. Do not heat your spectrometer or
chamber to 400°C
3. Find a reliable calibration working in the
same temperature range with a known
emissivity below 3 μm
4. Put everything in a nice looking box
Planetary Emissivity Laboratory
Lets turn up the heat – and keep everything else cold!
Jörn Helbert [email protected]
Planetary Emissivity Laboratory
Characterisation of thermal behavior
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
460.6°C –
standard dev 3.1°C
Helbert and Maturilli, 2009
Playing with Quartz in the mid-infrared –
Not
good
Venus butuseless
always for
a good
test
case
Maybe
notfor
completely
Venus
after
all…
Planetary Emissivity Laboratory
• There is a clear
change of the
spectral behaviour
with temperature
• No shift of the
position of the
emissivity maximum
or the reststrahlen
band is observed
Jörn Helbert [email protected]
• The shape of the
reststrahlen band
changes significantly
Helbert and
Maturilli 2009
• We see a shift in the
position of the
transparency
features
The problem: Our calibration source could not go beyond 175°C
A „cold“ 175°C calibration source does not help with
measurements for VEX VIRTIS
Jörn Helbert [email protected]
While the raw data shows a
good signal for hot samples the
„cold“ blackbody can not be
measured…
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
Linearity of the response function
Planetary Emissivity Laboratory
Helbert and Maturilli, 2009
Evaluating a possible calibration source
Jörn Helbert [email protected]
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
With this blackbody we could finally try to
calibrate our emissivity measurements
Planetary Emissivity Laboratory
We were getting close already in Dec
Current limit of usable S/N ratio
„VIRTIS“ windows
Jörn Helbert [email protected]
Planetary Emissivity Laboratory
The next step is only days away –
The planetary simulation chamber
Planetary Emissivity Laboratory
• Vacuum(!?!)
• Internal calibration
sources
• Induction heating
• A lot of temperature
sensors
Jörn Helbert [email protected]
• Automatic sample
transport system
• All components are
separately tested
• Easily adaptable!
Jörn Helbert [email protected]
Getting the last items done –
BBQing a new blackbody coating
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
Manufacturing and testing is finished
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
Automatic sample transport system
Planetary Emissivity Laboratory
New sample cups
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
• Higher thermal stability
• A modified version with a
window can be used to
measure (and transport)
weathered samples in a
Venus-like atmosphere
Conclusions
Planetary Emissivity Laboratory
Jörn Helbert [email protected]
• Obtaining emissivity measurements for samples at 500°C is a tricky
task, but we managed (see Helbert et al. 2009)
• Obtaining emissivity measurements at 1μm for samples at 500°C is a
very tricky task
• We are getting close, however we can not yet give any indication for
the „red“ or „blue“ material
• Once the basic setup is working we need to perform extensive tests
• Then the fun part begins:
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Selection of analog materials
Characterisation of changes in the materials
Characterisations of mixtures
Test of different hypothesis for the interpretation of VIRTIS data
Support for future missions and instrument development
• Finally - include the temperature as another parameter in the Berlin
Emissivity Database (Maturilli et al. 2008)
SurVenTIS –
Surface of Venus Thermal Imaging System
• Basic design idea is a CCD
imager with a filter wheel
Planetary Emissivity Laboratory
Electronics box
• Proposed filter
Jörn Helbert [email protected]
Wheel drive
1.02 µm +
0.85, 0.90,
1.10, 1.18 µm
Surface imaging
1.31 µm
Cloud imaging –
cloud correction for
surface imaging
0.77 µm
Constrain albedo vs.
absorption
0.65 µm
Fe3+ band,
oxidation state of
the surface
Neutral
„Grayscale imaging“
– cloud morphology
and public outreach
Black
Flatfielding and
calibration
Filter wheel
CCD/CMOS
detector 256x256
10°-15° wide
angle optics
VIRTIS
Mass of 31kg
SurVenTIS
Mass > 1kg