‘Super-antenna’ could let Mars rover talk directly with Earth

 Right now, Mars rovers like Curiosity get roughly 15 minutes to talk to scientists back on Earth, twice per day. 

If a scientist wants to issue a complex set of orders, or download a whole bunch of new information, it has to all fit into these 15-minute windows.


 For scientists on the ground, the necessity of bouncing signals through multiple orbiting satellites means that rover missions progress as a series of quick snapshots, with tense waits in between. Now, they have a prototype for a new and improved type of rover antenna, one that could turn those minutes into hours, and those orbiters into space junk.
The idea comes from a group working on advanced antenna technology at UCLA, in combination with NASA’s Jet Propulsion laboratory.

The idea is basically to use an array of 256 antenna elements (a 16 x 16 square) all working together to make a “super-antenna” capable of directly communicating with Earth. Having fewer moving bodies to worry about keeping in alignment, this system could give a rover up to several hours of communication time with operators back on Earth, every day.


The reason it works is not just that the array of mini-antennas creates a more powerful signal, but that the signal is circularly polarized. This has the effect of keeping the signal coherent as it travels through the Martian atmosphere — once a signal gets into the vacuum of space with good signal strength intact, getting the rest of the way to an orbiter around the Earth isn’t hard at all.
Amazingly, this huge increase in signal strength will still run within the power limitations of NASA’s upcoming Mars 2020 rover: it has only about 100 watts to allot to communications, or about enough to keep an incandescent lightbulb shining. For that power commitment, it will purportedly be able to maintain a signal with a satellite around Earth, 225 million kilometers away. The 2020 mission may well be NASA’s major precursor to the start of a manned mission, so it will important to see if it can serve as a proof of concept for direct communications between the Earth and Mars.

The additive characteristics of its compound antenna actually work in both directions; not only will it be able to create more powerful signals to transmit back to Earth, but it will be able to pick up more powerful signals as well. This will give it a better ability to download information from the Earth, widening the lines of communication for both scientists and their rover.
The Mars 2020 rover won’t have the luxury of twisting around to make sure it’s pointing at the Earth at every moment, and so the antenna is planned to be mounted on a gimbal arm that can lift the antenna and orient it in any direction. This unrestrained antenna mount, combined with the circular polarization of the signal itself, should also allow the rover to transmit and receive while on the move, meaning that those hours of phone time don’t need to be wasted.
Right now, the UCLA team has only made a four-element-by-four-element prototype. But this prototype behaved just the way their simulations expected, and as it had to if their 16-by-16 version was going to work. A full-scale prototype is in the works.