1. Polar Orbiting INfrared Tracking Receiver Overall Mission Review
Stanford Student Space Initiative, Satellites Team
Team Leads: Anjali Roychowdhury, Jake Hillard Faculty Advisor: Prof. Simone D’Amico Primary Author: Anjali Roychowdhury
Satellite Optical Communications
POINTR Ground to Space Demo
Essential Components
In order to effectively create a bidirectional optical communications link, our optical receiver needs to be able to accurately point to and track an incoming laser signal. To effectively demonstrate many of the challenges of an adequately robust and accurate pointing and tracking technologies, we’re building a 1U (10cm x 10cm x 10cm) optical receiver payload which will go into orbit February 2018 aboard Audacy’s satellite.
The laser beacon tracking phase begins as POINTR passes over San Francisco on its way to JPL’s OCTL on Table Mountain. As our payload becomes reachable via Audacy’s high-speed radio, we collect GPS data to direct JPL’s laser beacon in the direction of our satellite. Once POINTR’s sensors detect the location of the laser beacon, POINTR’s fine steering mirror aligns the beam on the tracking sensor. POINTR can also direct the satellite’s ADCS to turn the satellite toward the laser beacon if it starts to drift out of the receivers field of view. The satellite continues to point and track the laser from OCTL until it is too low on the horizon and OCTL is no longer visible.
The payload consists of an optical receiver, which is composed of a silicon photodiode and electronic amplification, a quad-cell receiver to measure the angle of arrival of the optical signal, a silicon MEMS mirror to perform fine optical steering, and a microcontroller based payload computer. In order to fit this entire assembly in the meager space we have, we’ve carefully designed our structural assembly and mounts for these parts to simultaneously minimize space and survive the harsh thermal, vacuum, shock, and vibration conditions of space.
Cubesat to Cubesat optical communications can enable new space science applications and space based networks.
With increasing data demands from imaging, communications, and scientific satellites, the speed limitations imposed by radio communications have become a bottleneck for progress. Transmitting information optically presents an attractive alternative because the savings in size, weight, and power are accompanied by a data rate boost of x that of typical radio links. Optical communications has successfully been demonstrated from large satellites, but little work has been demonstrated on a smaller scale. The development of cubesat optical communications will be exceedingly useful for smallsat project for large distributed networks.
Audacy is a space data and network service startup is providing us payload space on their 3U cubesatellite, and NASA JPL would provide the ground laser beacon from their Optical Communications Telescope Lab.
Block diagram and early CAD render of our optical payload.
POINTR proposed Concept of Operations (CONOPS).
Future Work
Moving forward, we will use POINTR’s pointing and tracking system and the experience gained from this mission to create two cube satellites to establish a bidirectional optical communications link in space. This further mission will launch within the next 2 years. We hope to be the first to demonstrate effective bidirectional optical communications on such a small Size, Weight, and Power (SWaP) scale.
Mission Partners