| MISSION_DESCRIPTION |
Most of the contents in this description are extracted from
[NAKAMURAETAL2011].
Mission Overview
================
AKATSUKI, also known as Venus Climate Orbiter (VCO) and PLANET-C
was successfully launched at 21:58:22 (UTC) on May 20, 2010 using the
H-IIA F17 Launch Vehicle. The main goal of the mission is to understand
the Venusian atmospheric dynamics, super-rotation, and cloud physics,
with the explorations of the ground surface and the interplanetary dust
also being the themes. The Venusian atmosphere was studied during the
Venus Express mission of the European Space Agency. AKATSUKI was also
designed to study the Venusian atmosphere, but in contrast to the Venus
Express strategy, five cameras with narrowband filters will image Venus
at different wavelengths to track the distributions of clouds and minor
gaseous constituents at different heights. In other words, we aim to
study the Venusian atmospheric dynamics in three dimensions, while Venus
Express collected mainly spectroscopic observations of the atmosphere.
The mission started with the mission name and the spacecraft name
``PLANET-C'', which means Japan's third planetary explorer succeeding
SUISEI (PLANET-A), which observed Halley's comet, and NOZOMI (PLANET-B),
which could not complete its mission to explore Mars. About half year
before launch, the Japan Aerospace Exploration Agency (JAXA) officially
decided the nickname of the PLANET-C as ``Venus Climate Orbiter'' and
also as ``AKATSUKI'' that is a Japanese word meaning ``dawn''.
After the successful cruise from Earth to Venus, which took about half a
year, the propulsion system malfunctioned during the Venus orbit
insertion (VOI) maneuver on December 7, 2010 [NAKAMURAETAL2011;
HIROSEETAL2012].
The orbital maneuvering engine (OME) was shut down at 158 s during VOI,
while 12 min of operation had been planned. Consequently, the spacecraft
did not attain Venus orbit; instead, it entered an orbit around the sun
with a period of 203 days.
The OME was ultimately found to be broken and unusable, but most of the
fuel still remained. Thus, a decision was made to use the reaction
control system (RCS) thrusters for orbital maneuvers in November 2011,
which were successfully executed so that AKATSUKI would re-encounter
Venus in 2015.
After the orbital maneuvers in November 2011, the orbital period became
199 days and the encounter with Venus was set for November 22, 2015.
This specific date was originally chosen to achieve the shortest
encounter time given the spacecraft's now limited expected lifetime.
However, a detailed trajectory analysis revealed that the orbit around
Venus after insertion on November 22, 2015, would be unstable.
Therefore, to achieve a more stable orbit, another orbital maneuver was
performed in July 2015 to set the spacecraft on a trajectory to meet
Venus on December 7, 2015, just 5 years after from the failure of the
VOI. After December 1, 2015, the spacecraft's orbit was just outside of
Venus's orbit and the velocity of the spacecraft relative to the sun was
less than that of Venus, which allowed Venus to catch up to the
spacecraft from the trailing side. On December 7, 2015, the spacecraft
approached the planet from outside of Venus's orbit and VOI-Revenge 1
(VOI-R1) procedure was implemented by using four 23 Newton class
thrusters of the RCS.
VOI-R1 burn (1228 s) was successfully achieved from 23:51:29 on December
6 through 00:11:57 on December 7 (UTC, onboard time). AKATSUKI is the
first Japanese satellite to orbit a planet. After the VOI-R1, the
apoapsis altitude was ~440,000 km with an inclination of 3 degrees and
orbital period of 13 days and 14 h. For the dual purposes of decreasing
the apoapsis altitude and avoiding a long eclipse during the orbit, a
trim maneuver was performed at the first periapsis. The apoapsis
altitude was ~360,000 km with a periapsis altitude of 1,000 -- 8,000 km,
and the period is 10.5 days.
On April 4, 2016, orbital maneuver PC1 was successfully achieved during
about 15 seconds to avoid long eclipses during the orbit. After the PC1,
the apoapsis altitude was ~370,000 km with a periapsis altitude of
1,000 -- 10,000 km, and the period is 10.8 days.
On October 7, 2020, orbital maneuver PC2 was successfully achieved
during about 4 seconds to avoid very long umbra and penumbra.
The mission has been described in many papers [OYAMAETAL2002;
ISHIIETAL2004; NAKAMURAETAL2007; NAKAMURAETAL2011; NAKAMURAETAL2014;
NAKAMURAETAL2016].
Science Goals
=============
Venus is one of the most attractive targets in the solar system when we
seek to understand how terrestrial planets differentiate into various
types. Venus is our nearest neighbor, and has a size very similar to the
Earth's. However, previous spacecraft missions discovered an extremely
dense (~92 bar) and dry CO2 atmosphere with H2SO4-H2O clouds floating at
45 -- 70 km altitudes, and exotic volcanic features covering the whole
planet. The abundant gaseous CO2 brings about a high atmospheric
temperature (~740 K) near the surface via greenhouse effect. The
atmospheric circulation is also much different from the Earth's.
AKATSUKI aims to solve the mystery of the atmospheric circulation and
cloud formation of Venus, with secondary targets being the exploration
of the ground surface and the zodiacal light observation during the
cruise to Venus. The exploration of the Venusian meteorology is
important not only for understanding the climate of Venus but also for a
general understanding of planetary fluid dynamics. AKATSUKI will explore
the Venusian atmosphere using a set of sophisticated optical instruments
dedicated to meteorological study and radio occultation technique. Such
an approach complements the Venus Express mission, which aimed to
understand the Venusian environment with a different approach.
Instruments
===========
The onboard science instruments altogether sense multiple height levels
of the atmosphere to model the three-dimensional structure and dynamics.
The lower atmosphere and the surface on the nightside are investigated
by the 1-um Camera (IR1). The altitude region from the middle and lower
clouds to 10 km below the cloud base on the nightside is covered by the
2-um Camera (IR2). The dayside middle and lower clouds are mapped by
IR1. The dayside cloud top is observed principally by the Ultraviolet
Imager (UVI) and also by IR2. The Longwave Infrared Camera (LIR) has an
ability to observe the cloud top of both dayside and nightside. The
Lightning and Airglow Camera (LAC) searches for lightning and maps
airglows on the nightside. Radio Science (RS) complements the imaging
observations principally by determining the vertical temperature profile
and its spatial and temporal variabilities using Ultra-Stable Oscillator
(USO). The typical altitude levels probed by the infrared wavelengths
are discussed by [TAKAGI&IWAGAMI2011].
IR1, IR2, UVI and LIR are cameras with large-format detector arrays, and
have much common features in the image data format. They are operated
sequentially as a unit in many cases. For these reasons, a dedicated
camera control unit called the Digital Electronics unit (DE) was
developed to conduct sequential exposures using these cameras and to
process the image data from these cameras before storing them in the
data recorder. The basic specifications of the cameras are summarized in
Table 1. The cameras have Field of Views (FOVs) of 12 degrees or larger;
given a FOV of 12 degrees, the full disk of Venus can be captured in one
image at distances of >8.5 Rv. Brief descriptions of the science
instruments are given below.
Table 1. Basic specifications of the instruments.
+---+--------+------------+------------------+---------+----------------+
|Cam|FOV(deg)|Detector |Filters |Bandwidth|Targets |
+===+========+============+==================+=========+================+
|IR1|12 x 12 |Si-CSD/CCD |1.009 um (night) |0.0391 um|Surface, Clouds |
| | |1024 x 1024 +------------------+---------+----------------+
| | | pixels|0.969 um (night) |0.0386 um|H2O vapor |
| | | +------------------+---------+----------------+
| | | |0.898 um (night) |0.0289 um|Surface, Clouds |
| | | +------------------+---------+----------------+
| | | |0.900 um (day) |0.0091 um|Clouds |
| | | +------------------+---------+----------------+
| | | |0.750 um, Diffuser|0.4000 um|(Flat field) |
+---+--------+------------+------------------+---------+----------------+
|IR2|12 x 12 |PtSi-CSD/CCD|1.735 um (night) |0.043 um |Clouds, |
| | |1024 x 1024 +------------------+---------+ Particle size |
| | | pixels|2.26 um (night) |0.058 um | |
| | | +------------------+---------+----------------+
| | | |2.32 um (night) |0.038 um |CO below clouds |
| | | +------------------+---------+----------------+
| | | |2.02 um (night) |0.040 um |Cloud-top height|
| | | +------------------+---------+----------------+
| | | |1.65 um (night) |0.300 um |Zodiacal light |
+---+--------+------------+------------------+---------+----------------+
|UVI|12 x 12 |Si-CCD |283 nm (day) | 13 nm |SO2 at cloud top|
| | |1024 x 1024 +------------------+---------+----------------+
| | | pixels|365 nm (day) | 15 nm |Unknown absorber|
| | | +------------------+---------+----------------+
| | | |320 nm, Diffuser | 100 nm |(Flat field) |
+---+--------+------------+------------------+---------+----------------+
|LIR|16.4 |uncooled |10 um (day/night) | 4 um |Cloud top |
| | x 12.4|bolometer | | |temperature |
| | |328 x 248 | | | |
| | | pixels | | | |
+---+--------+------------+------------------+---------+----------------+
|LAC|16 x 16 |8 x 8 |777.4 nm (night) | 9 nm |OI lightning |
| | |multi-anode +------------------+---------+----------------+
| | |avalanche |543 nm (night) | 136 nm |O2 Herzberg II |
| | |photodiode | | |airglow |
| | | +------------------+---------+----------------+
| | | |557.7 nm (night) | 5 nm |OI airglow |
| | | +------------------+---------+----------------+
| | | |545.0 nm (night) | 5 nm |(Background) |
+---+--------+------------+------------------+---------+----------------+
1-um Camera (IR1)
-----------------
IR1 [IWAGAMIETAL2011] was designed to image the dayside of Venus at
0.90 um wavelength and the nightside at 0.90, 0.97 and 1.01 um
wavelengths, which are located in the atmospheric windows
[TAYLORETAL1997]. These windows allow radiation to penetrate the
whole atmosphere.
The dayside 0.90 um images visualize the distribution of clouds
illuminated by sunlight. Although the dayside disk at this wavelength
appears almost flat, small-scale features with contrasts of ~3% are
observed and considered to originate in the middle and lower cloud
region [BELTONETAL1991]. Tracking of such cloud features provides the
wind field in this region.
On the nightside, IR1 measures the thermal radiation mostly from the
surface and a little from the atmosphere. The 0.97 um radiation is
partially absorbed by H2O vapor, and thus the comparison of this
radiance with radiances at other wavelengths allows the estimation
of H2O content below the cloud. Measurements at 0.90 and 1.01 um will
yield information about the surface material [BAINES2000;
HASHIMOTO&SUGITA2003], and are expected to find out hot lava ejected
from active volcanoes by utilizing the high sensitivity of the
radiance to temperature in this wavelength region
[HASHIMOTO&IMAMUR2001].
As imaging instruments, IR1 and IR2 have many common features. These
cameras share electronics for A/D conversion since the detector arrays
in these cameras are electronically nearly identical. Each of the
cameras consists of a large baffle which eliminates stray light from
the sun, refractive optics, a filter wheel, and a 1040 x 1040 pixels
detector array (1024 x 1024 area is used). The optics and the detector
array altogether yield an effective FOV of 12 degrees, giving the
pixel resolution of ~6 km from the distance of 5 Rv. The detector
array of IR1 is a Si-CSD (charge sweeping device)/CCD which is cooled
down to 260 K to achieve a signal-to-noise ratio of ~300 on the
dayside and ~100 on the nightside.
2-um Camera (IR2)
-----------------
IR2 [SATOHETAL2016] utilizes the atmospheric windows at wavelengths of
1.73, 2.26, and 2.32 um; the first two suffer only CO2 absorption,
while the last one contains a CO absorption band. At these wavelengths
the outgoing infrared radiation originates from the altitudes
35 -- 50 km.
To track cloud motions a series of 2.26 um images will be mostly used.
As the small-scale inhomogeneity of the Venusian cloud layer is
thought to occur predominantly at altitudes 50 -- 55 km
[BELTONETAL1991], the IR2 observations should yield wind maps in this
region. As CO is photochemically produced above the cloud and
subsequently transported to the deeper atmosphere (such sinks are not
yet precisely located), the distribution of CO should give us
information about the vertical circulation of the atmosphere. We will
extract the CO distribution at 35 -- 50 km altitudes by
differentiating images taken at 2.26 and 2.32 um [COLLARDETAL1993;
TSANGETAL2008]. To study the spatial and temporal variations in the
cloud particle size, the cloud opacities at 2.26 and 1.73 um, together
with the IR1 1.01-um and 0.90-um images, will be analyzed with the aid
of radiative transfer calculations [CARLSONETAL1993].
IR2 employs two additional wavelengths. At 2.02 um, which is located
in a prominent CO2 absorption band, we expect to observe the variation
of the cloud-top altitude as intensity variations of the reflected
sunlight similarly to the cloud altimetry by Venus Express VIRTIS
using the 1.6-um CO2 band [TITOVETAL2009]. The astronomical H-band
centered at 1.65 um aims at observing the zodiacal light.
IR2 utilizes a 1040 x 1040 pixels PtSi sensor (1024 x 1024 area is
used), which has advantages such as the high stability, uniformity and
durability against energetic radiation. The architecture of the device
is based on a technology of the 512 x 512 PtSi detector which was
applied to astronomical observations [UENO1996]. To suppress the
thermal electrons in the detector, it is cooled down to 65 K by a
Stirling cooler. Heat is also removed from the lens and lens housing,
making these components be cooled down to ~170 K. The resultant
signal-to-noise ratio is expected to be over 100 when imaging the
Venusian nightside.
For observing the zodiacal light, the camera optics is designed to
suppress the instrumental background as well as the stray light. The
large baffle of the camera is very useful for interplanetary dust
(IPD) observations, because it provides us with very wide coverage in
the solar elongation angle from 180 degrees (anti-solar direction) to
30 degrees. The PtSi sensor is specially designed to realize precise
measurements of the instrumental zero level. The stability of the zero
level is essentially important for the IPD observations, because the
target is extending beyond the instantaneous FOV of the camera.
Ultraviolet Imager (UVI)
------------------------
The solar ultraviolet radiation scattered from the Venusian cloud top
shows broad absorption between 200 nm and 500 nm wavelengths. SO2
explains the absorption between 200 nm and 320 nm, while the absorber
for >320 nm has not yet been identified [ESPOSITOETAL1997]. UVI is
designed to map the ultraviolet contrast at 283 nm for observing SO2
and at 365 nm for the unknown absorber.
UVI [YAMAZAKIETAL2018] will make clear the spatial distributions of
these ultraviolet absorbers and their relationships with the cloud
structure and the wind field. The tracking of ultraviolet markings
yields wind vectors at the cloud top [ROSSOWETAL1990]. The mixing
ratios of both SO2 and the unknown absorber are considered to increase
precipitously with decreasing the altitude below the cloud top
[POLLACKETAL1980; BERTAUXETAL1996], and thus the spatial distributions
of these species should be sensitive to vertical air motions
[TITOVETAL2008]. In addition to nadir-viewing observations, limb
observations will visualize the vertical structure of the haze layer
above the main cloud [BELTONETAL1991].
UVI utilizes an ultraviolet-coated backthinned frame transfer Si-CCD
with 1024 x 1024 pixels. Given the FOV of 12 degrees, the pixel
resolution is ~16 km at the apoapsis (distance of 13 Rv) and ~6 km
from the distance of 5 Rv. The signal-to-noise ratio is expected to be
~120 when viewing the dayside Venus.
Longwave Infrared Camera (LIR)
------------------------------
LIR [TAGUCHIETAL2007; FUKUHARAETAL2011] detects thermal emission from
the cloud top in a wavelength region 8 -- 12 um to map the cloud-top
temperature, which is typically ~230 K. Unlike other imagers onboard
AKATSUKI, LIR is able to take images of both dayside and nightside
with equal quality. The cloud-top temperature map will reflect mostly
the cloud height distribution, whose detailed structure is unknown
except in the northern high latitudes observed by Pioneer Venus OI
[TAYLORETAL1980] and the southern high latitudes observed by Venus
Express VIRTIS [PICCIONIETAL2007]. LIR has a capability to resolve a
temperature difference of 0.3 K, corresponding to a few hundred-meters
difference in the cloud height.
The images taken by LIR will visualize convective cells and various
types of waves within the cloud layer. Tracking of the movements of
blocky features will also yield wind vectors covering both dayside and
nightside. Such a full local time coverage has never been achieved in
the previous wind measurements, and will enable, for example, the
derivation of zonal-mean meridional winds for the first time.
The sensor unit of LIR includes optics, a mechanical shutter, an image
sensor and its drive circuit, and a baffle that keeps direct sunlight
away from the optical aperture. The image sensor is an uncooled micro-
bolometer array with 328 x 248 pixels for a FOV of 16.4 degrees x 12.4
degrees. Since the sensor can work under room temperature, huge and
heavy cryogenic apparatus which is usually necessary for infrared
devices is unnecessary. The frame rate of the image sensor is 60 Hz,
and several tens of images obtained within a few seconds will be
accumulated to increase the signal-to-noise ratio. Given the FOV of
12.4 degrees for 248 pixels, the pixel resolution is ~70 km on the
Venus surface when viewed from the apoapsis (13 Rv), and is ~26 km
from the distance of 5 Rv.
Lightning and Airglow Camera (LAC)
----------------------------------
LAC [TAKAHASHIETAL2008] searches for lightning flashes and maps
airglow emissions on the nightside disk of Venus when AKATSUKI is
located in the eclipse (umbra) of Venus. A major goal of the lightning
observation is to settle the controversy on the occurrence of
lightning in the Venusian atmosphere. The distribution of lightning,
if it exists, should reflect the microphysics of clouds and the
dynamics of mesoscale convection. The 777.4 nm [OI] line of atomic
oxygen is utilized for lightning observation, since this line is
considered as the most strong emission from lightning discharges
according to a laboratory experiment simulating the Venusian
atmosphere [BORUCKIETAL1996]. Possible lightning flashes were detected
on the nightside disk of Venus at this wavelength by using a
ground-based telescope [HANSELLETAL1995].
LAC also measures emissions in two airglow bands to study the
global-scale circulation and small-scale waves in the lower
thermosphere. One is the O2 Herzberg II emission centered at 552.5 nm
wavelength, which is considered a consequence of the recombination of
atomic oxygen in downwelling and is the strongest emission among the
visible Venusian airglows [SLANGERETAL2001]. The other is the 557.7 nm
[OI] emission; though Venera 9 and 10 failed to detect this emission
[KRASNOPOLSKY1983]. [SLANGERETAL2001; SLANGERETAL2006] observed it
using a ground-based telescope.
LAC has a FOV of 16 degrees. The detector is a multi-anode avalanche
photo-diode (APD) with 8 x 8 pixels of 2 mm square each. Among the
64 pixels of the APD, 4 x 8 pixels are allocated to 777.4 nm for
lightning detection, 2 x 8 pixels are allocated to 480 -- 605 nm for
O2 Herzberg II emission, 1 x 8 pixels are allocated to 557.7 nm
emission, and 1 x 8 pixels are used for an airglow-free background at
545.0 nm. These wavelengths are covered by using rectangular
interference filters fixed on the detector.
In the lightning observation mode, individual lightning flashes are
sampled at 32 kHz by pre-triggering. Lightning flashes with an
intensity of 1/100 of typical terrestrial lightning would be detected
when viewed from 1,000 km altitude. For mapping airglows, the Venusian
nightside is scanned by changing the direction of the FOV. The
detector's one pixel corresponds to 35 km resolution on the Venusian
surface viewed from 1,000 km altitude, and 850 km resolution from 3 Rv
altitude.
Ultra-Stable Oscillator (USO), used for Radio Science (RS)
----------------------------------------------------------
RS [IMAMURAETAL2011] aims to determine the vertical structure of the
Venusian atmosphere using radio occultation technique. In this
experiment, the spacecraft transmits radio waves toward the tracking
station (Usuda Deep Space Center of Japan) and sequentially goes
behind the planet's ionosphere, neutral atmosphere, and solid planet
as seen from the tracking station, and reemerges in the reverse
sequence. During such occultation events the neutral and ionized
atmospheres of the planet cause bending, attenuation and scintillation
of radio waves. The received signal is recorded with an open-loop
system and analyzed offline.
The frequency variation observed at the tracking station yields the
time series of the bending angle, from which the vertical profile of
the refractive index is derived. The refractive index profile yields
the temperature profile of the neutral atmosphere by assuming
hydrostatic balance [FJELDBOETAL1971]. The height range of the
Venusian neutral atmosphere accessible by radio occultation is
approximately 32 -- 90 km; below 32 km the radius of curvature of the
ray path becomes smaller than the distance to the planet center. The
ionospheric electron density profile is also derived from the
refractive index profile. From the observed signal power variation,
the sub-cloud H2SO4 vapor densities [JENKINSETAL1994] and the
intensity of small-scale density fluctuation [WOOETAL1980] are
obtained.
The uniqueness of AKATSUKI RS as compared to the previous radio
occultation experiments at Venus is that low latitudes can be probed
many times thanks to the near-equatorial orbit, so that broad local
time regions are covered. Another merit of AKATSUKI is that the
locations probed by RS can be observed by the cameras a short time
before or after the occultations.
An ultra-stable oscillator (USO) provides a stable reference frequency
which is needed to generate the X-band downlink signal used for RS.
The USO is a heritage from the USOs flown onboard the ESA's Rosetta
and Venus Express spacecraft [HAEUSLERETAL2006].
The instruments, with acronym and Principal Investigator (PI), are
summarized below:
Instrument Acronym PI
---------------------------- -------- ------------------
1-um Camera IR1 Naomoto Iwagami
2-um Camera IR2 Takehiko Satoh
Longwave Infrared Camera LIR Makoto Taguchi
Ultraviolet Imager UVI Shigeto Watanabe
Lightning and Airglow Camera LAC Yukihiro Takahashi
Ultra-Stable Oscillator USO (RS) Takeshi Imamura
Shared module for instruments
=============================
Digital Electronics unit (DE)
-----------------------------
DE is a controller for IR1, IR2, UVI and LIR. To conduct a set of
camera operations which is repeated many times (every 2 hours in
nominal global imaging), the main satellite system controller (Data
Handling Unit, DHU) triggers the DE unit. DE, then, sequentially
triggers detailed observation sequences of the cameras including
filter wheel and gain settings, exposure, and data transfer. DE is
also responsible for arithmetic data processing, data compression,
and telemetry data formatting and packeting.
To repeat a variety of observation sequences, each of which includes
complicated manipulations of multiple cameras as a unit, we prepared
a set of ``observation programs'' and installed them in DE. For
example, the ``dayside deluxe'' observation program setups the
cameras, takes images using all dayside filters of the four cameras
sequentially, conducts arithmetic data processing, compresses the
acquired image data, and shutdowns the cameras, within 26 minutes.
The observation programs will be updated several times during the
mission depending on the results of the observations.
The arithmetic data processing includes dark signal subtraction, dead
pixel correction, computation of median from multiple images,
averaging of images, and flat field correction. The data compression
method is either the lossless compression algorithm by the ``HIREW''
developed by NEC Ltd. [TAKADAETAL2007] which is also known as
``StarPixel Lossless'' or the JPEG2000 lossless/lossy compression
[BOLIEKETAL2000]. Since the derivation of wind vectors from high-
resolution cloud images might require high fidelity data acquisition,
we will use lossless data compression as far as possible. However, in
the epochs of low telemetry rate, lossy compression will also be
adopted.
Mission Phases
==============
CRUISE
------
Mission Phase Start Time : 2010-05-20
Mission Phase Stop Time : 2010-12-06
----------------------- ---------- -----------------------------------
Event Date Description
----------------------- ---------- -----------------------------------
Launch 2010-05-20 21:58:22 UTC, H-IIA F17 Launch
Vehicle, from Tanegashima Space
Center in Kagoshima, Japan.
Test maneuver (APH-1) 2010-06-28 10:00:00 UTC, the orbital
maneuvering engine (OME) was used
near aphelion during 13 seconds.
delta-V was 12.2 m/s. This maneuver
also served as a test of the OME.
Trim maneuver 1 (TRM-1) 2010-11-08 01:00:00 UTC, four RCS thrusters
were used during 21 seconds.
delta-V was 2.9 m/s.
Trim maneuver 2 (TRM-2) 2010-11-22 00:00:00 UTC, four RCS thrusters
were used during 2.125 seconds.
delta-V was 0.27 m/s.
Trim maneuver 3 (TRM-3) 2010-12-01 00:00:00 UTC, four RCS thrusters
were used during 0.375 seconds.
delta-V was 0.04 m/s.
SUN ORBITING
------------
Mission Phase Start Time : 2010-12-07
Mission Phase Stop Time : 2015-12-06
----------------------- ---------- -----------------------------------
Event Date Description
----------------------- ---------- -----------------------------------
Venus orbit insertion 1 2010-12-07 00:00:00 UTC, that is the closest
(VOI-1) time between Venus and the
spacecraft. The OME was started at
23:49:00 UTC on 2010-12-06 to enter
the orbit, but was shut down at 158
seconds, while 718 seconds of
operation had been planned. Planned
delta-V was 748 m/s, but achieved
delta-V was only 135 m/s. The VOI-1
was failed. The expected
communications blackout due to
occultation by Venus was from
23:54:00 to 00:12:02. After the
occultation, communications
blackout continued. The spacecraft
was found at 01:26:17, and entered
in heliocentric orbit with the
period of 203 days, perihelion
0.61AU and aphelion 0.74AU.
Superior-conjunction 2011-06-25 from 2011-06-17 to 2011-07-05,
command operation could not be
carried out.
Test maneuver 1 (TM1) 2011-09-07 02:50:00 UTC, OME was used during
2 seconds.
Test maneuver 2 (TM2) 2011-09-14 02:50:00 UTC, OME was used during
5 seconds.
Disposal of Oxidizer 2011-09-30 03:02:00 UTC, oxidizer was disposed
Test (DOX Test) during 60 seconds. delta-V was
1.9 m/s.
Disposal of Oxidizer 1 2011-10-06 02:53:00 UTC, oxidizer was disposed
(DOX1) during 360 seconds. delta-V was
7.6 m/s.
Disposal of Oxidizer 2 2011-10-12 03:23:00 UTC, oxidizer was disposed
(DOX2) during 540 seconds.
Disposal of Oxidizer 3 2011-10-13 04:53:00 UTC, oxidizer was disposed
(DOX3) during 540 seconds. Total delta-V
of DOX2 and DOX3 was 16 m/s.
Delta-V 1 (DV1) 2011-11-01 04:22:00 UTC, four RCS thrusters
were used during 587 seconds.
delta-V was 88.6 m/s.
Delta-V 2 (DV2) 2011-11-10 04:37:00 UTC, four RCS thrusters
were used during 544 seconds.
delta-V was 90.6 m/s.
Delta-V 3 (DV3) 2011-11-21 04:57:00 UTC, four RCS thrusters
were used during 342 seconds.
delta-V was 63.5 m/s.
Superior-conjunction 2015-02-11 from 2015-02-05 to 2015-02-14,
command operation could not be
carried out.
Delta-V 4-1 (DV4-1) 2015-07-17 04:00:00 UTC, four RCS thrusters
were used during 93 seconds.
delta-V was 17.5 m/s.
Delta-V 4-2 (DV4-2) 2015-07-24 04:00:00 UTC, four RCS thrusters
were used during 303 seconds.
delta-V was 56.3 m/s.
Delta-V 4-3 (DV4-3) 2015-07-31 04:00:00 UTC, four RCS thrusters
were used during 74 seconds.
delta-V was 13.6 m/s.
Trim maneuver 2015-09-11 02:30:00 UTC, four RCS thrusters
for VOI-R1 (TRM-R1) were used during 6.4 seconds.
delta-V was 1.1 m/s.
PRIMARY SCIENCE PHASE
---------------------
Mission Phase Start Time : 2015-12-07
Mission Phase Stop Time : 2018-03-31
----------------------- ---------- -----------------------------------
Event Date Description
----------------------- ---------- -----------------------------------
Venus orbit insertion, 2015-12-07 00:00:00 UTC, four RCS thrusters
Revenge (VOI-R1) were used during 20 min and 28
seconds. delta-V was 134.8 m/s. The
spacecraft successfully entered the
orbit. The apoapsis altitude was
~440,000 km with an inclination of
3 degrees and orbital period of 13
days and 14 h.
+Y-axis inversion 2015-12-09 23:36:00 UTC, from south to north.
Maneuver for phase 2015-12-20 14:11:00 UTC, four RCS thrusters
control (VOI-R2) were used during 94 seconds.
+Y-axis inversion 2016-02-08 23:16:00 UTC, from north to south.
Maneuver for phase 2016-04-04 07:28:00 UTC, four RCS thrusters
control (PC1) were used during 15 seconds.
delta-V was 2.2 m/s.
Superior-conjunction 2016-06-07 from 2016-05-29 to 2016-06-15,
command operation could not be
carried out.
+Y-axis inversion 2016-11-24 05:00:00 UTC, from south to north.
+Y-axis inversion 2017-02-01 04:30:00 UTC, from north to south.
+Y-axis inversion 2017-11-16 01:00:00 UTC, from south to north.
Superior-conjunction 2018-01-09 from 2017-12-29 to 2018-01-21,
command operation could not be
carried out.
+Y-axis inversion 2018-02-23 03:00:00 UTC, from north to south.
EXTENDED SCIENCE PHASE 1
------------------------
Mission Phase Start Time : 2018-04-01
Mission Phase Stop Time : 2021-03-31
----------------------- ---------- -----------------------------------
Event Date Description
----------------------- ---------- -----------------------------------
+Y-axis inversion 2018-04-04 05:41:00 UTC, from south to north.
Long umbra and penumbra 2018-07-29 Umbra and Penumbra
12:00 -- 15:48 UTC (~228 min)
Umbra
12:37 -- 15:05 UTC (~148 min)
Long umbra and penumbra 2018-08-09 Umbra and Penumbra
04:31 -- 06:45 UTC (~133 min)
Umbra
04:36 -- 06:37 UTC (~120 min)
+Y-axis inversion 2018-10-04 04:00:00 UTC, from north to south.
Long umbra and penumbra 2019-01-19 Umbra and Penumbra
23:32 -- 02:09 UTC (~156 min)
Umbra
23:43 -- 02:01 UTC (~138 min)
Long umbra and penumbra 2019-01-30 Umbra and Penumbra
11:06 -- 16:08 UTC (~302 min)
Umbra
12:01 -- 15:20 UTC (~199 min)
+Y-axis inversion 2019-02-06 00:00:00 UTC, from south to north.
+Y-axis inversion 2019-06-19 03:30:00 UTC, from north to south.
Attitude anomaly event 2019-08-11 until 2019-09-04T03:00:00, the
spacecraft was off-nominal
attitude.
Superior-conjunction 2019-08-14 from 2019-08-07 to 2019-08-21,
command operation could not be
carried out.
+Y-axis inversion 2020-03-05 06:15:00 UTC, from south to north.
+Y-axis inversion 2020-07-28 02:00:00 UTC, from north to south.
Maneuver for phase 2020-10-07 12:22:00 UTC, four RCS thrusters
control (PC2) were used during 4 seconds.
delta-V was 0.52 m/s.
Long penumbra 2020-12-15 Penumbra
15:38 -- 22:30 UTC (~412 min)
Long penumbra 2020-12-24 Penumbra
21:35 -- 01:45 UTC (~250 min)
+Y-axis inversion 2021-01-21 01:50:00 UTC, from south to north.
Superior-conjunction 2021-03-26 from 2021-03-19 to 2021-04-03,
command operation could not be
carried out.
EXTENDED SCIENCE PHASE 2
------------------------
Mission Phase Start Time : 2021-04-01
Mission Phase Stop Time : 2024-03-31 (planned)
----------------------- ---------- -----------------------------------
Event Date Description
----------------------- ---------- -----------------------------------
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