Akatsuki, IKAROS & Others

Planet-C or VCO (Venus Climate Orbiter, renamed Akatsuki after launch) is a Japanese Space Agency (JAXA) mission to study the dynamics of the atmosphere of Venus from orbit, particularly the upper atmosphere super-rotation and the three-dimensional motion in the lower part of the atmosphere, using multi-wavelength imaging. It will also measure atmospheric temperatures and look for evidence of volcanic activity and lightning. The scientific payload consists primarily of cameras in the near-infrared range. The Planet-C main bus is a 1.6 m × 1.6 m × 1.25 m box with two solar array paddles, each with an area of 1.4 square meters, on opposite (+y and -y) sides and a 1.6 m high gain antenna on the +x side. On the opposite side (-x) from the antenna is a 0.45 m long orbital maneuvering engine. The total launch mass of the spacecraft will be 640 kg, including 320 kg of propellants and 34 kg of scientific instruments. The spacecraft was to go into a near equatorial Venus orbit with an apoapsis of about 60,000 to 80,000 km and a very low periapsis. On 7 December 2010, Akatsuki failed to enter orbit around Venus due to a malfunction in the propulsion system. An unexpected pressure drop in the spacecraft's fuel line, or possibly damage to the probe's engine nozzle, are the likely causes. JAXA plans to manoeuvre the probe to try it again five years later. Tests of the engine in September 2011 resulted in low thrust. The back-up option is to use the RCS for orbit insertion. To enable this, the oxidizer needs to be dumped to reduce the weight of the probe. This will result in a less than optimal orbit. On 7 December 2015, another attempt to enter orbit was successful, this time using the RCS thrusters. It entered a 400 km × ~440000 km orbit of ~3° inclination with an orbital period of 13 days and 14 hours.

The IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is a experimental a solar sail. It is the world's first solar powered sail craft employing both photon propulsion and thin film solar power generation during its interplanetary cruise. IKAROS was launched together with Planet C (VCO, Akatsuki) from the Tanegashima Space Center using the H-2A-202 launch vehicle. After separation from the carrier rocket, it spun at up to 20 rpm, deploying the membrane and generating solar power by means of thin film solar cells (minimum success level) within several weeks. Acceleration and navigation using the solar sail will then be demonstrated (full success level) within half a year. The shape of the membrane is square, with a diagonal distance of 20m. It is made of polyimide a mere 0.0075 mm thick. In addition to the thin film solar cells, the steering devices and dust-counter sensors are fitted to the membrane. The membrane is deployed, and kept flat, by its spinning motion. Four masses are attached to the four tips of the membrane in order to facilitate deployment. Deployment is in two stages. During the first stage, the membrane is deployed statically, and during the second stage, dynamically. This deployment method can be realized with simpler and lighter mechanisms than conventional mast or boom types as it does not require rigid structural elements. After successfully unfolding the solar sail IKAROS deployed two tiny subsatellites called DCAM 1 and 2 to photograph the deployed sail.

The UNITEC 1 (UNISEC Technology Experiment Carrier), also named Shin'en, was a satellite (or “an artificial planet” as it escapeed the Earth gravitational field) built by UNISEC, a collaboration between several Japanese universities. It was launched into Venus transfer orbit by H-2A-202 launch vehicle with the main payload of Planet-C Venus orbiter developed by JAXA on May 2010. It has the following engineering missions: - Onboard computers developed by several universities will be tested in the harsh space environment in the form of a competition; i. e., the computer which can survive to the last in the radiation-rich deep space environment will win the competition. - Technologies to receive and decode very weak and low bit rate signal coming from deep space will be developed and experimented. - Technologies to estimate orbit and signal Doppler shift of the satellite based on the received RF signal will be developed and experimented. These technologies are essential for tracking and receiving signals from a satellite in deep space. UNITEC-1 carried communication equipment working in the 5.8 GHz amateur bands. The transmission output was about 15 W. UNITEC-1 has been developed by 20 universities of UNISEC (University Space Engineering Consortium), which is Japanese university community developing nano-satellites. Contact with the spacecraft was established after launch, but was lost shortly after.

The Waseda-SAT2 is a nanosatellite built by students of the Waseda University for Earth observation and technology demonstration. The 1U CubeSat features a camera for Earth observation. It was to test the use of extendible paddles to provide attitude control. The satellite was one of a number of secondary payloads on the H-2A-202 rocket, which launched the Planet C Venus orbiter. Contact with the satellite was not established after launch.

Negai✰ (Negai-Star or Negai-Boshi, formerly known as Excelsior) is a CubeSat mission built by Soka University. It is a space verification of an advanced information processing system using commercial FPGA. The satellite was one of a number of secondary payloads on the H-2A-202 rocket, which launched the Planet C Venus orbiter.

KSAT (Kagoshima Satellite, also named Hayato) is a small 1U CubeSat mission developed by the Kagoshima University, which has following objectives: Observation experiments of atmospheric vapor distribution for predicting localized heavy rain Shooting moving images of the Earth through microwave high-speed communications Basic communication experiment for super-small positioning satellites The satellite was one of a number of secondary payloads on the H-2A-202 rocket, which launched the Planet C Venus orbiter. Contact with the satellite was not established after launch. An improved version was built as KSAT 2 (Hayato 2).

The IKAROS solar sail craft deployed two tiny subsatellite cameras called DCAM 1 and 2 to monitor the success of the deployment process of the solar sail. Each of the DCAMs featured a camera and was battery powered and had an operating time of 15 minutes.