Science Concept Information Sheet
Break-out:
Venus
Form completed by: Eliot Young
Concept title (ID): Venus Daytime Cloud Circulation (15)
Description of the potential science / science goals:
Observe Venus' upper cloud deck (~65 - 70 km) in wavelengths from 0.36 to 1 µm. These observations
enable cloud tracking studies (as proxies for wind vectors) and tracking of the unknown UV absorber.
Relevance of the science (Why is this important?) What are the specific Decadal ties?
Addresses several questions raised in the Decadal Survey (see p. 121):
(1) How do clouds influence radiative balance in Venus' atmosphere?
(2) How does Venus' global circulation differ from that of Earth and Mars?
(3) What are the key processes, reactions and chemical cycles controlling the chemistry of the lowermiddle-upper atmosphere of Venus?
What measurements are required to achieve the science?
Imaging of Venus cloud tops in about 4 - 10 narrow band filters from 0.36 to 1 µms
What are the driving requirements to achieve the measurements? (E.g. time on target, frequency of
observations, aperture, focal length, wavelengths, pointing precision and stability, specific observing
location(s), critical observation time(s), are repeat flights required? or whatever else that may drive the
hardware or mission design/architecture).
Telescope aperture:
1m
1m class aperture achieves 0.09" resolution imaging at 0.36 µm, equivalent to about 18 km on Venus at
inferior conjunction, or ~30 km at 6-8 from weeks away from conjunction. A balloon-borne platform,
tracking cloud features for several (5+) hours continuously, could track cloud features well below the
sub- 1 m/s level, sufficient to characterize meridional motion and possibly sufficient to characterize
angular momentum transport by comparing instantaneous to average u and v velocities.
Telescope focal length: about 40m
Wavelengths: 0.36 - 1.0 µm
Pointing precision: 0.05".
Required time on target: 20 -40 days. Images in all filters can be obtained in tens of minutes, but a
baseline of several hours is necessary to get reliable cloud motion rates. Total mission durations of 20 to
40 days (centered on inferior conjunction) are necessary to look for planetary wave phenomena that are
predicted in GCMs.
Are there other ways to achieve this science, and if so, why would a balloon platform be preferable?
The JAXA/VCO mission would have provided images of Venus at 0.36 µm that would have provided
excellent cloud tracking but VCO did not enter orbit around Venus. Venus Express VMC instrument is still
providing images of Venus' southern hemisphere. Groundbased observations can image Venus' northern
hemisphere, but retrieve much coarser rates that available from a balloon. A balloon mission is strongly
preferred for three reasons: (1) long, uninterrupted observing baselines of several hours are essential to
determine cloud motions at the 1 m/s level and better, (2) a mission duration of 20 - 40 continuous days
is necessary to characterize planetary wave phenomena, and (3) The diffraction limited resolution of a
1m balloon (0.1") provides 25x more resolution elements over Venus' disk than a groundbased image
taken in good seeing conditions (0.5" assumed).
What are the potential observation targets?
Venus between quadratures and inferior conjunction.
What planetary science disciplines would this involve?
Planetary Atmospheres, comparative planetology
Point of contact for follow-on questions (Name and contact info)
Eliot Young (efy@boulder.swri.edu, 720-432-2333)