Much like what NASA did when Neil Armstrong became the first man on the moon, NASA wants to transmit a live feed of the first man on ‘Mars’. But unlike the quality of video that appeared back in 1969, NASA wants to capture High Definition video in greater details that will be transmitted to the Earth when the first man walks on the surface of the Mars. Although it’s plausible, it is a tough task to achieve. Scientists at NASA have been experimenting with laser lights to transmit data from Mars to Earth that will be mounted atop Psyche spacecraft expected to launch for Mars in 2022.
NPR reported details on ‘Lunar Laser Communication Demonstration’ in 2013 when NASA demonstrated how it can transmit HD video from Moon to the Earth in real time. But there is a massive difference between sending data from Moon to the Earth compared to Mars to the Earth and it is due to the humongous distance between these two neighboring planets. As per Kevin Kelly, CEO of LGS Innovations, Herndon, the distance between Earth and the Moon is feeble 240,000 miles while its increases exponentially to over 140 million miles to the red planet. Kelly’s company is planning to integrate laser light technique in its Psyche mission which is a part of Deep Space Optical Communications.
When seen from Mars, Earth appears as a small dot i.e. Pale Blue Dot. When pointing laser towards the Earth, the distance plays a major role in the transmission. Even at the speed of light, it takes around 20 minutes for the laser to arrive towards the intersection point on Earth one-way. Meanwhile, the Earth which is revolving around its axis is 20 minutes apart from its location 20 minutes ago. Although the laser beam can reach the probe, it is difficult to gauge the location to transmit the signal from Earth to the probe. To explain it, consider the time taken by the beam to reach Earth is 20 minutes, which means that the Earth has already displaced from its original place 20 minutes ago.
This is where ‘Point ahead’ system is used. Although there are many complexities with the system, the basic idea revolves around pointing the signal towards a location where the Earth would be 20 minutes later. Consider a point A and B where A is the spacecraft and B is the point on Earth where the beam will be transmitted. Now, the spacecraft will have to exercise its point ahead system and point out the direction of the beam towards A+20 minutes i.e. the point on Earth after 20 minutes. The interception of the signal from such a long distance is another challenge. NASA has proposed to use 200-inch Hale telescope mounted on Mt. Palomar in California to detect even the faintest signal on the factor of a single photon.
A similar experiment will be conducted by MIT’s Lincoln Laboratory in 2019 where they will send a prototype system in the low-earth orbit to transmit data to and fro. Since the distance between the surface and the probe is negligible compared to Earth and Mars’ distance, it would take a small 4 to 8 inches telescope to intercept the signal sent.
Although transmitting data and video over light beam may sound new, it is an old concept used by Alexander Graham Bell who invented ‘Photophone’ in the 1880s. The system would transfer sound using light beam from the sun. He even demonstrated his invention by transmitting data from a school near White House to his laboratory few blocks away. NASA will launch the communication system aboard Psyche spacecraft in 2022.