Professor Kazuya Yoshida is in charge of the Space Robotics Laboratory
at Tohoku University's Department of Aerospace Engineering. He and
Professor Yukihiro Takahashi of Hokkaido University's Department of
Cosmosciences began working together almost a decade ago on the development
of microsatellites for science missions. Prof. Takahashi played a major role in
selecting scientific missions and served as science mission coordinator for the
"RISING" series of microsatellites, among other things, while he was at
Tohoku University, too. These two partners formed a team from the Graduate
School of Engineering and the Graduate School of Science.
The "RISING" (Sprite-Sat) microsatellite was successfully launched into a
670 km high, sun-synchronous orbit in January, 2009. It went up as a piggyback
payload aboard a Japanese H-IIA launch vehicle. RISING is about 50 x 50 x 50 cm,
and weighs about 45 kg.
"RISING" is derived from RAIJIN, the god of thunder and lightning in
Japanese mythology, for reasons that will become obvious in a moment.
"The goal of this satellite is to establish key technologies for a
university-based, 50kg-class of micro-satellites and to conduct
scientific observation of 'sprites' which are a type of Transient
Luminous Event (TLE) observed in the middle atmosphere. TLE's were
first discovered in 1989, and they typically occur at an altitude of
40 km to 90 km," said Prof. Yoshida. "It is considered that large scale
thunderstorms are capable of producing such luminous events over the
clouds, but a true mechanism is still under the veil."
Prof. Takahashi added that in order to clarify the mechanism of TLEs,
observing horizontal structures of TLEs is considered to be essential.
"RISING and RISING-2 carry two cameras with different filters to
capture the TLEs in the direction of their nadirs. Other satellite
projects are proceeding which use the same type of imagers such as
TARANIS at CNES, ASIM / ISS at ESA, and FORMOSAT-5 in Taiwan. Also, our
Japanese team has just completed the fabrication of the Global
Lightning and SprIte Measurements (GLIMS / JEM-EF or GLIMS / ISS)
experiment which will be installed soon on the Japanese Experiment
Module - Exposed Facility attached to the International Space Station,"
said Prof. Takahashi.
GLIMS is scheduled to be launched this winter.
One of the major advantages of microsatellites in general is their
relatively quick turnaround time or development to launch cycle.
"RISING was the first microsatellite to be launched (for the purpose
described above). Even GLIMS, whose development is based entirely on
the heritage of RISING, emerged earlier than the other missions," said
Prof. Takahashi.
See http://www.astro.mech.tohoku.ac.jp/SPRITE-SAT/index_e.html
Prof. Yoshida emphasizes that while RISING has experienced a crippling
blow as a result of a failed power control system, the engineering
verification of the key technologies for future microsatellites was
otherwise almost a complete success.
"The spacecraft is alive and in orbit now, but more than 930 days after
the launch, no scientific observations have been conducted yet due to
the problem caused by the power failure," said Prof. Yoshida.
RISING-2 is the exact same size and weight as RISING. Fabrication and
evaluation tests of the engineering model, and verification of the
flight model were finished by May. Evaluation tests and updating of
on-board software are continuing. There is no firm launch date.
RISING-2 features a telescope that is 10cm in diameter and has a 1m
focal length, and it take images with 5m resolution. It can generate
multi-spectrum images using a liquid crystal tunable filter as well as
Red-Green-Blue color photos.
"The primary mission is the observation of cumulonimbus clouds in
visible, near infrared. Also, TLEs in the upper atmosphere such as
sprite are observed using complimentary metal oxide semiconductor -
based sensors," said Prof. Yoshida.
Why would someone study thunderstorms and cumulonimbus clouds - hence
the RAIJIN connection?
"The development mechanism is very difficult to observe and gaining
more knowledge about these clouds, given their important role as
significant carriers of water vapor which is the dominant greenhouse
gas, is vital to increasing our understanding of the dynamics of
climate change," said Prof. Takahashi. "This detailed observation
may be only made possible via a microsatellite that can be operated on
demand by a scientist."
More specifically, this telescope images at any wavelength in
the 650-1050 nanometer range using a liquid crystal filter for the
first time. This enables its operators to measure the absorption line
of water vapor around a thundercloud, which is a result of updrafts
which are essential to thunderstorm activity.
"This telescope can be useful for many other important purposes
including the estimation of carbon fix, and observation of planetary
phenomenon such as cloud heights and cloud structures on Jupiter, for
example," said Prof. Takahashi.
RISING-2's power control system, which caused such a problem on the
previous satellite, has been much improved to ensure the system's
reliability.
"A new 3-axis attitude sensing and control system, including sun
sensors, star trackers, reaction wheels and an on-board computer
dedicated to attitude control, was also developed. This one differs
from the original installed on RISING which relied on passive
gravity-gradient plus active damping control" said Prof Yoshida.
The Rapid International Scientific Experiment Satellite (RISESAT) will
be this team's third 50 kg-class demonstration microsatellite, and it
counted as one of the 5 satellites that will be developed under the
"New-Paradigm of Space Development and Utilization by Nano-Satellite"
program led by Prof. Nakasuka at the University of Tokyo with funding
support from the Cabinet Office, Government of Japan.
(See the discussion of the"Hodoyoshi" program in Part 1 where RISESAT
was identified as "Hodoyoshi-2")
RISESAT will carry 8 scientific instruments with a total mass of 10 kg
- the preliminary design review was completed recently - developed by
the following countries: Sweden, Czech Republic, Hungary,
Taiwan(China), Vietnam, USA and Germany. These were selected from 17
candidates who responded to the RISESAT open call. The instruments
include a High Precision Telescope, a 3D Magnetometer, a 3D Cosmic
Radiation Sensor, and a Meteor Detector.
The onboard telescope is a successor to the RISING-2 telescope. A
Japanese science team will support ongoing development, operation and
analysis activities. The main objectives are astronomical observation
and forestry surveillance in collaboration with the requisite
Taiwanese, Vietnamese and Japanese agencies.
The team's 10 x 10 x 20 cm Cube-Sat called RAIKO weighing 2 kg will be
deployed from the International Space Station next year. RAIKO means a
drum that is carried by RAIJIN. This project is a collaboration with
Wakayama University and the University of Tokyo.
"The mission is a technology demonstration which will verify some
components that will be useful for future micro and nano satellites,"
said Prof. Yoshida.
"Microsatellites in the 50 kg range with dimensions roughly 50 x 50 x
50 cm have a great potential for significant scientific observation and
remote-sensing missions, while Cube-Sats are mostly useful for
technology demonstration and education."
"Today, the commercial and government markets for small satellites in
the 100 kg to 300 kg category are growing rapidly, and in this domain,
some pioneering companies, such as UK-based SSTL, are already
successful," said Prof. Yoshida. "Japan has a chance to be successful
in the markets involving much smaller satellites with a 50 kg maximum
weight. This market is not yet well established commercially."
Japan has always excelled at anything involving miniaturization and
Japan's list of creative breakthroughs in this regard is long indeed.
If it can be made lighter, smaller, and more economically-efficient,
Japan can figure out how to do it. Japan's formidable and agile
knowledge-intensive industrial base plays a fundamental role here.
"The Japanese government is very supportive of this concept and our 3
microsatellites - RISING, RISING-2 and RISESAT - are all funded by
government programs. Development costs range approximately between $USD
1.5 - 3.8 Million. Typical development time is 1.5 to 2 years," said
Prof. Yoshida.
He is excited that these 3 microsatellites are contributing to
breakthroughs in scientific and remote sensing types of applications
such as climate and disaster monitoring as well as the comprehensive
investigation of carbon circulation mechanisms beginning with the
observation of TLEs, cumulonimbus clouds and thunderstorms.
When exactly will the launches of RISING-2 and RISESAT take place?
"The number of flight opportunities provided by JAXA is very limited.
RISING-2 is now registered by JAXA as a candidate of future launch, but
no suitable launch options for our mission exist prior to 2013," said
Prof. Yoshida. "As for RISESAT, most likely we will use a commercial
launcher such as a Russian Denpr or an Indian PSLV. But to make it
happen we need to obtain the necessary funds to cover the launch cost,
which is rising steadily these days."
Prof. Yoshida is glad that so many eager researchers from other
countries are now emerging. That said, an intensive search is underway
for partners - especially in SE Asia - for the University International
Formation Mission (UNIFORM) microsatellite project that Japan announced
last year.
Sweden's AAC Microtec provided the on-board avionics technology that
was installed on RISING. And AAC's space plug-and-play avionics
solution will be handling the interfacing of the multiple scientific
instruments aboard RISESAT, too.
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