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Utilizing Space Through Satellites Super Low Altitude Test Satellite "TSUBAME" (SLATS)

Operation Completed

About Super Low Altitude Test Satellite "TSUBAME" (SLATS)

Creating new possibilities in satellite usage by developing new orbits

The Super Low Altitude Test Satellite "TSUBAME" (SLATS) is the first Earth observation satellite to use a super low orbit. A "super low orbit" refers to an orbit with an altitude lower than 300 km. This orbit is an undeveloped region and it has yet to be fully utilized by satellites. Satellites in a super low orbit will bring benefits such as high resolution observations for optical imagers, low power transmissions for active sensors, and cost reductions for satellite manufacturing and launches. This is due to the closer range to the Earth.
A satellite in a super low orbit like SLATS will be exposed to air resistance, which is approximately 1,000 times greater than that of most Earth observation satellites at an altitude of 600 to 800 km. Consequently, this type of satellite will require a greater amount of fuel than conventional satellites. In order to solve the atmospheric drag issue, JAXA has adopted an ion engine. The ion engine uses fuel 10 times more efficiently than gas jets. Furthermore, we are developing a compact satellite to minimize air resistance, and will verify that our technology can support orbiting at super low altitudes over an extended period of time.
Then JAXA will take the first step toward practical application of a super low altitude satellite.

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Dec. 24, 2017 Updated

SHIKISAI and TSUBAME critical operation phase successfully completed! Initial function verification starts!

SHIKISAI and TSUBAME critical operation phase successfully completed! Initial function verification starts!

JAXA received telemetry data from SHIKISAI and TSUBAME, confirming that their satellite attitude control system had transitioned to the steady state. Current status of both satellites is stable. Subsequently, the following procedure occurred - power generation that supports the satellites’ operation by the deployed solar array wings, ground communications and sound attitude control that maintains those operations. Combined by the completion of the series of other operations, such as powering u...

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Characteristics of Super Low Altitude Test Satellite "TSUBAME" (SLATS)

SLATS will use the ion engine technology developed by JAXA in order to verify its technology for orbit control at super low altitudes.
The test satellite will also collect technical data related to the atmosphere, which will be used in the design of future satellites.
Furthermore, SLATS will photograph the Earth, and its technology will be evaluated for future Earth observation satellites.

Ion engine
For a super low altitude satellite, strong thrusters are not required, although atmospheric resistance increases. A thrust equivalent to the weight of one small coin such as a dime is sufficient. A long-life and high-fuel efficiency thruster is required. An ion engine is the most appropriate type of space engine, when considering these conditions.
From the perspective of exerting the greatest possible thrust, the propellant used in the SLATS ion engine is xenon gas, which is the same propellant that was used in Hayabusa. Furthermore, SLATS uses technology developed for KIKU No. 8, which realizes greater thrust than Hayabusa.

Atomic oxygen monitoring system
The atmosphere becomes denser as we come closer to the surface of the Earth, and a substance called "atomic oxygen" increases at super low altitudes. Atomic oxygen is known to damage 1tte golden thermal control films (Multi-Layer Insulation) that are used for satellites.
Normally, oxygen gas consists of two atoms which enter a covalent bond and form a molecule. Atomic oxygen refers to a state in which oxygen gas separates due to space radiation and ultraviolet rays, existing as a single atom. This makes atomic oxygen highly reactive and causes it to damage material used on the surface of satellites.
For SLATS, countermeasures have been taken such as applying a coating which is highly resistant to atomic oxygen to the outer surface of the multi-layer insulation. SLATS is also equipped with an atomic oxygen monitoring system which measures the concentration of atomic oxygen and the deterioration of materials when reacting with atomic oxygen. The acquired data will be used in the design of future super low altitude satellites.

Major Characteristics

Major onboard instruments 1. Atomic Oxygen Monitoring System
a) AOFS (Atomic Oxygen Fluence Sensor)
b) MDM (Material Degradation Monitor)
2. OPS (Optical Sensor) for Earth observation
Size 2.5 (X) x 5.2 (Y) x 0.9 m (Z)
（when expanded in orbit)
Weight 383 kg
Generated power 1,140 W or more
Design life 2 years or longer
Results of Orbital Maintaining Operation Tsubame successfully completed its orbital maintaining operation using ion engine
technology at all the seven altitudes as follows:
271.5 and 216.8 km each for 38 days, and
250, 240, 230, 181.1 and 167.4 km each for 7 days.
(At 167.4 km altitude, Tsubame used both its ion engine system and RCS because of the large atmospheric drag.)
Launch Date 10:26:22 on December 23, 2017 (JST)
Launch Vehicle H-IIA F37
Operation End Date October 1st, 2019

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