What are Optical Payloads?
Air-to-ground (ATG) and space-to-ground communications are continually evolving, and with technological developments entering the marketplace at an advanced rate, the interaction between airborne and ground stations have become more refined in recent years. There is, however, a constant need for further growth concerning ATG and space-to-ground communicative abilities. Recent announcements such as in-flight 5G ATG networks by 20211 and the USA army’s call for systems that support ATG network integration2 demonstrate both the necessity and progression of better communication.
Optical payloads are just one example of how communications are being improved between space to earth. The term ‘payload’ is theoretically defined as a vehicle’s revenue-producing cargo; however, in terms of aerospace, the name denotes the elements of a spacecraft that have been specifically designed to generate mission data and transmit it back to earth. In the case of optical payloads, these are components that have been deployed to produce and deliver mission-specific data — this could include information for monitoring and observation purposes as well as communicative motives.
An advanced form of optical payloads was investigated by NASA research and development centre, the Jet Propulsion Laboratory (JPL), in 2014 as a way of assessing technology for laser communication systems. The spacecraft instrument, named OPALS (an acronym for Optical PAYload for Lasercomm Science), discarded traditional radiofrequency (RF) communications and opted for an alternative with the ability to transport data at a much faster rate. Hosted onboard the International Space Station (ISS), OPALS utilised a 2.5-watt, 1550nm laser to beam information from spacecraft to ground3, resulting in a first-of-its-kind, high-rate laser-based transfer of a 175-megabit video entitled ‘Hello World’.
By using an adaptive optics instrument, comprising mirrors and a high-speed camera, OPALS could recognise the atmospheric variations between its position and the California-based receiver, the Optical Communications Telescope Laboratory (OCTL), and correct any signal distortions4.
In more recent years, laser-based technologies have stepped forward as a new method of transmitting data, circumventing the traditional radiofrequency (RF) technique. According to a 2018 article published by NASA, laser communication technology is “more secure” and minimises “the potential for outside interference to space signals”5. The alternative method of interaction is also recognised for its narrower and more focused beam when compared to using RF waves, resulting in higher speed and greater accuracy.
Optics and Lasers Unite to Drive Communication
The satellite industry is incessantly changing, and with the advantageous opportunities offered by optical technology and laser-driven systems, more space-based innovations are emerging. For example, only last month, Europe launched a second satellite to join its laser communications network, which uses optical beams via a 1.8-gigabit laser to extract data from adjacent spacecraft and transmit it back to the ground. This is accomplished in approximately a 15-minute period, which, compared to the circa hour-plus delay transmission could take using a radio-receiving dish, is a vast improvement6.
Discernibly, where lasers are concerned, optics habitually make up a portion of the system, and with laser-based technology on the rise, the industry has switched on to the benefits of using optical techniques. Another form of optically-driven data transfer that has recently been merited for its high-speed connectivity is free-space optical communication (FSO) — a line-of-sight technology which uses laser beams to provide optical bandwidth connections. The marketplace for FSO has significantly developed, so much so that a 2018 market research report predicted an expected increase from $116.9m in 2016, to $1,748.0m in 20237.
Aiding the Military and Defence Sectors
Enhanced communications are not the only profit to derive from optical payloads. Closer to home, ‘electro-optical’ (EO) payloads are being used for several air-, ground- and seaborne military and defence applications such as intelligence, surveillance, target acquisition and reconnaissance (ISTAR) operations. Electro-optics such as infrared, multispectral and hyperspectral sensors as well as visible-light cameras are being integrated into aircraft, maritime vehicles and unmanned aerial vehicles (UAVs) to lead military observation, surveillance and targeting.
UAV payloads have also gained momentum in recent years, and the market is expected to garner $7,018m by 20228. Drone payloads can be categorised as optical-based mechanisms such as cameras and sensors and — specific to the military and defence fields — weapon systems and missiles.
The Future of Optical Payloads
Vast development, ongoing prototyping and state-of-the-art applications would not be possible without the use of photonics, and progressions are repeatedly growing. With the rising demand for larger capacity telecommunication satellites and the call for enhanced terrestrial and extra-terrestrial communications beckoning, optical technologies have, so far, made a considerable impact on methods of space-to-ground and ATG interaction.
With substantial improvements made across a relatively short timeframe and further innovations being explored across the aerospace, military and defence industries; the future looks bright for optical payloads, and to be a part of the revolution of improved communications, observation and surveillance is an exhilarating prospect.