Astrionics: Electronics For Space

Dr. S. S. VERMA; Department of Physics, S.L.I.E.T., Longowal; Distt.-Sangrur (Punjab)-148 106

2019-06-08 11:28:43



Space exploration with the help of efficient, reliable and safe technological advances has already become a common thing with the advanced countries.  Not only the results coming out of these explorations are looked upon with a high level of accuracy but exploration has been made safe for machines and men also. Electronics has a great role in all space exploration vehicles, their launching, journey, proper installation and control in the orbits, taking data/pictures and transmitting the same back to earth and coordination of each and every activity of these space vehicles. Spacecraft instrumentation includes the design, development, installation, and use of electronic, optical, gyroscopic, and other instruments that play a role in the control of the spacecraft, or that function to measure, record, display, or process different values or quantities encountered in the flight of a spacecraft.

Electronics is the enabling technology behind space exploration, satellite navigation and telecommunications. Astrionics is the science and technology of the development and application of electronic systems, sub-systems, and components used in spacecraft. The electronic systems on board a spacecraft include attitude determination and control, communications, command and telemetry, and computer systems. Astrionics includes the design, manufacture, or use of devices for the purpose of measuring, detecting, controlling, computing, recording, or processing data related to the operation of space vehicles or platforms. For engineers one of the most important considerations that must be made in the design process is the environment in which the spacecraft systems and components must operate and endure. The challenges of designing systems and components for the space environment include more than the fact that space is a vacuum.

Vital role of electronics play in apace

One of the most vital roles electronics and sensors play in a mission and performance of a spacecraft is to determine and control its attitude, or how it is orientated in space. The orientation of a spacecraft varies depending on the mission. The spacecraft may need to be stationary and always pointed at Earth, which is the case for a weather or communications satellite. However, there may also be the need to fix the spacecraft about an axis and then have it spin. The attitude determination and control system ensures that the spacecraft is behaving correctly. Further developments in space electronics need to cover a broad range of technology areas and products e.g., radiation hardened electronics, high performance processing, reconfigurable electronics, low temperature radiation hardened electronics etc. Advances in space robotics technology hinge to a large extent upon the development and deployment of sophisticated new vision-based methods for automated in-space mission operations and scientific survey.

Command and telemetry system

Another system which is vital to a spacecraft is the command and telemetry system, so much in fact, that it is the first system to be redundant. The communication from the ground to the spacecraft is the responsibility of the command system. The telemetry system handles communications from the spacecraft to the ground. Signals from ground stations are sent to command the spacecraft what to do, while telemetry reports back on the status of those commands including spacecraft vitals and mission specific data. The purpose of a command system is to give the spacecraft a set of instructions to perform. Commands for a spacecraft are executed based on priority. Some commands require immediate execution; other may specify particular delay times that must elapse prior to their execution, an absolute time at which the command must be executed, or an event or combination of events that must occur before the command is executed.Spacecraft perform a range of functions based on the command they receive. These include: power to be applied to or removed from a spacecraft subsystem or experiment, alter operating modes of the subsystem, and control various functions of the spacecraft guidance and altitude control system. Commands also control booms, antennas, solar cell arrays, and protective covers. A command system may also be used to upload entire programs into the RAM of programmable, micro-processor based, onboard subsystems.

The telemetry system is responsible for acquisition from the sensors, conditioners, selectors, and converters, for processing, including compression, format, and storage, and finally for transmission, which includes encoding, modulating, transmitting and the antenna. Commands to a spacecraft would be useless if ground control did not know what the spacecraft was doing. Telemetry includes information such as:

  • Status data concerning spacecraft resources, health, attitude and mode of operation
  • Scientific data gathered by onboard sensors (telescopes, spectrometers, magnetometers, accelerometers, electrometers, thermometers, etc.)
  • Specific spacecraft orbit and timing data that may be used for guidance and navigation by ground, sea, or air vehicles
  • Images captured by onboard cameras (visible or infrared)
  • Locations of other objects, either on the Earth or in space, that are being tracked by the spacecraft
  • Telemetry data that has been relayed from the ground or from another spacecraft in a satellite constellation

Sensors in space

Sensors can be classified into two categories: health sensors and payload sensors. Health sensors monitor the spacecraft or payload functionality and can include temperature sensors, strain gauges, gyros and accelerometers. Payload sensors may include radar imaging systems and IR cameras. While payload sensors represent some of the reason the mission exists, it is the health sensors that measure and control systems to ensure optimum operation.

Developments in spacecraft electronics

By adapting existing silicon-germanium (SiGe) technology, scientists have developed a transistor that can withstand the extreme conditions of deep space, without altering its original composition. The work exploits the natural benefits of the SiGe alloy, such as lighter weight and higher durability, to develop new circuit design models. Researchers claim that as SiGe can withstand the adverse conditions of space, much of the protective wiring and radiation shielding currently required could be dispensed with and electrical units could be located anywhere on the vehicle, providing an ‘environmentally invariant electronics platform. Silicon-germanium combines both materials in an epitaxial layer at nanoscale dimensions. The researchers were able to prove it can function in extreme space environments, where radiation from galactic cosmic rays and solar wind, as well as the extreme temperatures (from -230˚C to 120˚C), normally pose problems.  In the more distant future, a smaller electronics printer could be packed aboard a spacecraft and print electronics on demand. One of the big benefits of printed electronics is that there is no waste. Printable electronics are made with only the necessary materials, meaning there is no extra stuff for an astronaut to worry about. Electronics manufacturers would also no longer have to worry about building parts that can withstand the vibration and other rigors of the launch into space.