Mars to get comms upgrade with ExoMars mission

NASA radios due for in-flight test in May

When the European Space Agency's ExoMars mission rode the fire and set out on a seven-month trip to Mars, it also carried a telecommunications upgrade for the Red Planet's satellite networks.

Two Electra radios form part of NASA's participation in the project, carried on the Trace Gas Orbiter (TGO) to improve communications with the lander the expedition plans to drop in the Schiaparelli region.

The UHF radios are designed to adjust their data rates depending on their position relative to Schiaparelli: bandwidth will be higher when the orbiter is overhead, but throttled back when it's close to the horizon.

NASA says using relays achieves much higher data rates than would be possible if a lander tries to communicate directly from the surface of Mars.

While Electra radios have already been deployed to Mars in Curiosity and aboard the Mars Reconnaissance Orbiter for data relays, the radios travelling with ExoMars have around double the older versions' signal strength.

Bandwidth constraints are a big issue for deep-space communications. For example, the Phoenix surface mission that landed in 2008 could transfer just 250 MB a day on average. New Horizons famously manages just 1 Kbps from its vast distance.

Using relays has another advantage: it means a much smaller and lighter radio can be used on the lander, which represents real dollars in launch costs.

As NASA notes, the TGO's orbit is similar to that of the Mars Reconnaissance Orbiter, and is a “relay-favourable” near-circular orbit 400 km (250 miles) in altitude.

“TGO's main X-band radio will use a dish antenna 87 inches (2.2 meters) in diameter to communicate with Earth-based antenna networks operated by ESA, NASA and Russia”, NASA notes.

The radios will get their first in-flight test in about six weeks. ®

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