Using Photonic Propulsion and Computer Vision to Explore Deep Space

Rosa Li
4 min readAug 23, 2020

A few years ago, I went camping with my family. We went kayaking, fishing and made smores but out of all the fun activities, the one I remember most vividly is staring at the night sky.

Away from all the light pollution, I remember seeing the stars gleaming in the night sky. This sparked my interest in learning what lies outside of mother Earth. What is out there?

Humanity’s Quest in Discovering the Universe

From discovering fire or inventing the steam engine, humans have made substantial advancements in technology. Voyager 1 is around 17 billion km away from Earth and has provided scientists with so much information about magnetic fields, cosmic rays, charged particles, plasma etc.

Voyager 1

Photonic Propulsion

The concept of using photonic propulsion in deep space is quite new and it has not been used very often. Lightsail 1, Lightsail 2 and IKAROS are some of the few solar sails that have been deployed. Despite this, photonic propulsion is quite promising because it does not require the spacecraft to bring fuel. Photonic propulsion also allow spacecrafts to travel at around 10% the speed of light. To put into perspective how fast that is, current propulsion methods allow spacecrafts to travel at not even 1% the speed of light.

Photonic propulsion is usually used with solar sails. These are large, thin and reflective sheets of polymers such as Mylar which use momentum from photons to propel forward. To capture enough momentum, solar sails have large surface areas ex. LightSail 2 has a surface area of 32 m² (around the size of a football field).

PLP (Photonic Laser Propulsion) and PTFF (Photon Tether Formation Flight) are also methods that use the momentum of photons to propel spacecraft. PLP uses a very powerful laser that is aimed at a spacecraft. Such a high concentration of photons will allow a spacecraft to accelerate very quickly. PTFF is similar to PLP in that a very strong laser will be aimed at a spacecraft, supplying it with a high concentration of photons that will allow the spacecraft to accelerate at very high speeds. However, PTFF will use a network of small lasers that unite to form a larger laser. These methods, however, require infrastructure that is not yet available.

The solar sails can be maneuvered by changing the angle of the sail with respect to the sun. This can be done with autonomous navigation using an onboard atomic clock (discussed below).

Autonomous Navigation

A key motivation for developing autonomous software in space is communication latency and bandwidth. It takes 19 hours for Voyager 1 to send data to Earth!

Atomic Clocks

NASA has built a Deep Space Atomic Clock that will allow spacecrafts to travel much farther as it allows for the spacecraft to autonomously determine where it is located.

Watches and atomic clocks keep time in similar ways, however, atomic clocks are much more precise and more resistant against environmental factors. Both determine how much time has passed by sending an electric pulse through a quartz crystal. The crystal will vibrate at a steady frequency and the number of seconds that passed is determined by the frequency of light released by the quartz molecules. Since all quartz emit light at the same frequency, this method it is an accurate way to determine the time. Most atomic clocks have an additional feature where caesium atoms will be excited by the light emitted by the quartz molecules. The caesium atoms will proceed to hit a detector. If there is something wrong with the light emitted by the quartz crystal, caesium atoms will stop hitting the detector. The clock will sense that this is a problem and adjust the electrical impulses until caesium atoms start hitting the detector. The Deep Space Atomic Clock replaced caesium with mercury.

Deep spacecrafts that have been previously launched use large antennas on Earth to send signals to spacecraft, which then send those signals back to Earth. Atomic clocks on Earth measure how long it takes the signal to make this two-way journey. Then, human navigators on Earth use large antennas to tell the spacecraft its location and where it should go.

NASA realized that if humans should travel farther in space, a more efficient navigation method would need to be implemented. The Deep Space Atomic Clock will eliminate the need for the two-way signal. It will receive a signal from Earth and immediately be able to determine its location and where it should go next.

Future of Deep Space Exploration

The Deep Space Atomic Clock is currently in orbit around the Earth for testing and demonstration, however, scientists plan to implement the atomic clock in future deep space missions as a more efficient way to explore deep space.

Using photonic propulsion and atomic clocks, humanity will come closer to answering the question What is out there?