Current Status of Venus
orbiter Akatsuki
Takeshi Imamura (JAXA, Japan)
and AKATSUKI Project Team
Venus orbiter Akatsuki
•! Science target : ‘Weather of Venus’
–!
–!
–!
–!
–!
–!
Mechanism of ‘super-rotation’
Structure of meridional circulation
Meso-scale processes
Formation of clouds
Lightning
Active volcanism, inhomogeneity of surface material
•! Akatsuki was proposed in 2001 with strong support by
international planetary science community and approved as a
JAXA mission soon after the proposal.
•! Akatsuki was launched in May 2010. The Venus orbit insertion
scheduled for December 2010 has failed. Now Akatsuki is
orbiting the Sun.
AKATSUKI under integration
Lightning and
Airglow Camera
Ultra-Stable Oscillator
Mid-IR Camera
UV Imager
1µm Camera
2µm Camera
3D observations
Akatsuki
Temperature and H2SO4
vapor profiles (RS)
Airglow NLACO
Sulfur dioxide
NUVIO
90 km
Cloud temperature
NLIRO
Lower clouds
NIR1, IR2O
65 km
Wind vectors
50 km
Carbon monooxide
NIR2O
Lightning NLACO
Water vapor
NIR1O
35-50 km
Stratosphere
Clouds
Troposphere
Surface
Active volcanoes / Minerals
NIR1O
Observations to be conducted during
one orbital revolution of Akatuki
Successive Global images
of atmosphere and ground
surface (~24 hours)
Limb images
(~0.5 hour)
Orbital period in original
plan: 30 hours
Temperature / H2SO4
vapor / Ionosphere
by radio occultation
Close-up images/
Lightning/Airglow
(~3 hours x 2)
Complementary missions
AKATSUKI
Venus Express
Instruments
5 cameras
Radio science
Target
Atmospheric
dynamics
3 spectrometers
1 camera
Plasma analyzer
Magnetometer
Radio science
Atmospheric chemistry and
dynamics, Surface
processes, Plasma
environment
Orbit
Equatorial
Polar
Akatsuki launch: May 21, 2010
Separation
from H-IIA
Integration
Launch by H-IIA from
Tanegashima Space Center
Failure of Venus orbit insertion on Dec 7, 2010
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AKATSUKI will meet
Venus in 5-6 years
[AU]
Propulsion
system
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Current status of Akatsuki (1)
!! Failure of Venus orbit insertion
The Venus orbit insertion scheduled for December 2010 has
failed due to a malfunction of the main thruster. Now Akatsuki is
orbiting the Sun. There is a possibility of conducting Venus orbit
insertion again in 2015 or later.
!! Breakdown of the main thruster
The main thruster is unable to use according to the test of the
thruster conducted in September 2011. We decided to use the
attitude control thrusters (or the reaction control system, RCS)
to reach Venus again in 2015.
!! Disposal of oxidizer
The oxidizer for the main thruster was disposed in October.
Akatsuki has successfully reduced its weight by 65 kg.
Current status of Akatsuki (2)
!! Orbit control maneuver using small thrusters
For the rendezvous with Venus in 2015, Akatsuki has
successfully performed orbit control maneuvers with !V of
~260 m/s in total using the attitude control thrusters on
November 1, 10, and 21.
!! Condition of the spacecraft
All subsystems, except the main thruster, are normal. We
are carefully monitoring the long-term change of their
temperatures.
!! Expected orbit around Venus
It is still uncertain whether the orbit will be polar or
equatorial. The apoapsis will be higher than the original (>
300,000 km).
Thermal condition
Solar flux (W/m2)
Akatsuki perihelion
(0.6AU) 3655W/m2
Launch
(May 21)
Venus orbit (0.7AU)
2649W/m2
Perihelion
(April 17)
VOI
(Dec 7)
Earth orbit 1400W/m2
Date
13
Venus seen from Akatsuki 2 days after
the failure of Venus orbit insertion
365 nm (UVI)
10 µm (LIR)
0.9 µm (IR1)
Distance : 600,000 km
Analyses of the images are ongoing
Example : Improvement of the spatial resolution of
the LIR 10µm image by using multiple frames taken
under varying spacecraft attitude Venus photometry campaign from distances of
~13,000,000 km in March and May 2011
•! Science targets:
–! Phase angle-dependence of the disk-averaged brightness
to constrain the cloud structure
–! Detection of planetary-scale brightness variations with
time scales of several days at wavelengths of 283 nm, 365
nm, 0.9 µm, 2.02 µm and 10 µm
•! Images were obtained roughly one per day
2.02 µm (IR2)
365 nm (UVI)
Examples of the result: UV Light curves
DN
365 nm green
283 nm red Feb 26
55°
Mar 12
45°
30°
13°
Mar 26
9°
Apr 9
Date
Apr 23
30°
Phase angle (deg)
May 7
May 21
60° 61° 63°