Japanese research satellite to use magnetic read only memory (MRAM) to hunt sprites in the upper-atmosphere

Sprites, the somewhat whimsical name given to complex upper-atmosphere optical flashes known as transient luminous events (TLE), were first photographed by Space Shuttle astronauts on Oct. 21, 1989, although apocryphal sightings by military and commercial pilots had been reported earlier. Scientific understanding of these short-lived electrical phenomena, however, is practically nil.
By Control Engineering Staff March 1, 2008

Sprites, the somewhat whimsical name given to complex upper-atmosphere optical flashes known as transient luminous events (TLE), were first photographed by Space Shuttle astronauts on Oct. 21, 1989, although apocryphal sightings by military and commercial pilots had been reported earlier. Scientific understanding of these short-lived electrical phenomena, however, is practically nil.

Scientists at Tohoku University in Sendai, Miyagi Prefecture, Japan led by Prof. Yoshida Kazuya plan to change that by launching a satellite called SpriteSat. The spacecraft is one of six small satellites to be launched aboard an H-IIA rocket in summer 2008 by the Japan Aerospace Exploration Agency (JAXA).

One of the spacecraft’s significant experiments will rely on an emerging technology for its memory. That emerging technology is magnetic random access memory (MRAM), which combines magnetic materials and silicon integrated circuitry to form a fast, reliable, non-volatile RAM (NVRAM).

Sprites (also called “red sprites”) occur above thunderstorms prior to the familiar lightning discharges seen in the middle and lower atmosphere. Unlike those more familiar discharges, sprites (along with related phenomena called blue flashes and jets) move upward from the thunderstorm tops toward the stratosphere instead of downward toward the ground.

Capable of mounting a long-term observation program, SpriteSat will carry a magnetometer subsystem dubbed Tohoku-AAC MEMS Unit (TAMU). TAMU will provide SpriteSat with magnetometer data of the Earth’s magnetic field to correlate with its sprite observations.

Built by Ångström Aerospace Corp. (ÅAC) of Uppsala, Sweden, TAMU will record its observations in an extended temperature range 4 Mb MRAM from Freescale Semiconductor in Orlando, FL. Ångström selected Freescale’s device because it combines non-volatile memory with extended temperature operation, unlimited endurance, and long-term data retention, even when the power fails.

“Freescale’s 4 Mb MRAM device replaces both flash and battery-backed SRAM in Angstrom’s module for the SpriteSat,” said Dr. Johan Akerman, head of the Applied Spintronics Group at Sweden’s The Royal Institute of Technology in Kista, who helped design and build the electronics package. “The ability to reconfigure critical programs and route definitions during various stages of a satellite mission is a significant benefit.”

The MRAM stores program data and FPGA configuration data on a single memory, allowing Angstrom Aerospace to reduce all storage requirements to one chip, reducing board area. At the same time, the flexibility of MRAM storage allows the system to be reconfigured in space.

MRAM uses magnetic materials combined with conventional silicon circuitry to deliver the speed of SRAM with the non-volatility of flash in a single, unlimited-endurance device. MRAM devices combine the best features of non-volatile memory and RAM to enable “instant-on” capability and power loss protection in new classes of intelligent electronic devices. MRAM devices are used in a variety of applications, such as networking, security, data storage, gaming and printers. The extended temperature version is suitable for use in rugged application environments, such as military, aerospace and automotive designs.

Freescale introduced the MR2A16A 4 Mb device in 2006 as the world’s first commercially available MRAM for customers looking for an alternative that could replace flash, SRAM and EEPROM with a single chip and eliminate battery-backup for SRAM. Since then, the product has garnered several awards from many trade publications serving the embedded and industrial sectors.

www.freescale.com

www.aaerospace.com