Digital signal processors could form a vital part of NASA’s space program this year. A series of probe launches to the Moon and Mars will rely on the technology for sending data back to mission control. Devices supplied by Texas Instruments (TI) have been designed into the Spacecraft Transponding Modem (STM), a unit developed by NASA and research partners at Caltech for use in deep-space.
“One of NASA’s objectives has been to reduce the power consumption of deep-space communications,” says Tom Engibous, TI’s CEO. “Increasing solar power to handle these communications would have been cost-prohibitive, so the agency chose to reduce the power needed instead.”
According to NASA, the STM is smaller and less power hungry than traditional deep-space transponders. It has been designed to perform all of functions of a standard space modem, as well as handling coding, decoding and time-tagging. The modem also features an integral command detector, code-block processor and hardware command decoder, while functions such as turnaround ranging, regenerative pseudo-noise ranging and differential one-way ranging have also been built-in.
NASA is planning two launches to Mars in May and June this year and they are due to arrive early in 2004. They will be carrying a wide range of sensing equipment. All data captured will have to be sent back using the DSP-based modem.
The STM will track an X-band uplink signal from Earth and transmit back using both X-band and Ka-band downlinks. X-band are 3 cm waves operating at 10 GHz, while Ka-band describes 30 GHz uplink, 20 GHz downlink technology.
Data can be transmitted by any of three different phase-modulation schemes at rates from 5 bit/s to 24 Mbit/s.
Some of the ideas developed for use in the modem are expected to find use in consumer electronics of the near future. NASA has a history of trailblazing new technologies, with its past demands for reliable wireless communications and better imaging being translated into today’s wireless and portable multimedia devices.
In the same way, turbo coding is expected to find use in coming generations of cell phones to further reduce energy consumption while delivering higher levels of performance. “When you talk about going to Mars, it redefines what you mean by a wide area network,” says Engibous.