Small satellites: current status and emerging trends

SMALL SATELLITES: CURRENT STATUS AND EMERGING TRENDS: CURRENT STATUS AND EMERGING TRENDS

Dmyrto Bakhtin, Volodymyr Yakobnyuk

Faculty of the aviation and space systems, NTUU “KPI”

By exploiting enormous commercial investments, we can now build highly capable small, low-cost and reliable satellites built using the latest COTS terrestrial technologies.

Miniaturized satellites or small satellites are artificial satellites of low mass and size, usually under 500 kg (1,100 lb). While all such satellites can be referred to as small satellites, different classifications are used to categorize them based on mass (see below).

One reason for miniaturizing satellites is to reduce the cost: heavier satellites require larger rockets with greater thrust which also has greater cost to finance. In retrospect, smaller and lighter satellites require smaller and cheaper launch vehicles and can sometimes be launched in multiples. They can also be launched ‘piggyback’, using excess capacity on larger launch vehicles. Miniaturized satellites allow for cheaper designs as well as ease of mass production, although few satellites of any size other than ‘communications constellations’ where dozens of satellites are used to cover the globe, have been mass-produced in practice.

Besides the cost issue, the main rationale for the use of miniaturized satellites is the opportunity to enable missions that a larger satellite could not accomplish, such as:

  • Constellations for low data rate communications
  • Using formations to gather data from multiple points
  • In-orbit inspection of larger satellites.
  • University Related Research

A number of commercial and military-contractor companies are currently developing microsatellite launch vehicles to perform the increasingly-targeted launch requirements of microsatellites. While microsatellites have been carried to space for many years as secondary payloads aboard larger launchers, the secondary payload paradigm does not provide the specificity required for many increasingly sophisticated small satellites which have unique orbital and launch-timing requirements.

In July 2012, Virgin Galactic announced LauncherOne, an orbital launch vehicle designed to launch «smallsat» payloads of 100 kilograms (220 lb) into low-Earth orbit, with launches projected to begin in 2016. Several commercial customers have already contracted for launches, including GeoOptics, Skybox Imaging, Spaceflight Services, and Planetary Resources. Both Surrey Satellite Technology and Sierra Nevada Space Systems are developing satellite buses «optimized to the design of LauncherOne.» Virgin Galactic has been working on the LauncherOne concept since late 2008.

In December 2012, DARPA announced that the DARPA ALASA program would provide the microsat launch vehicle booster for another DARPA program that is intending to release a «constellation of 24 micro-satellites (~20 kilograms (44 lb) range) each with 1-meter imaging resolution».

There is a global nanosatellite movement, encouraged by the emergence of COTS solutions, turnkey solutions, launch brokers, nano/micro technology development, and overall non aerospace technology advancement that may account for bringing in new customers for new applications (including more commercial operators).

Future space telescopes with aperture diameter of over 20 metres will require assembly in space. High-precision formation flying has very high cost and may not be able to maintain stable alignment over long periods of time. Autonomous assembly is a key enabler for lower cost approach to large telescopes.

Larger satellites usually use monopropellants or bipropellant combustion rockets for propulsion and attitude control; these systems are complex and require a minimal amount of volume to surface area to dissipate heat. These systems are used on larger microsats, while other micro/nanosats have to use electric propulsion, compressed gas, vaporizable liquids such as butane or carbon dioxide or other innovative propulsion systems that are simple, cheap and scalable.

Microsats can use conventional radio systems in UHF, VHF, the S-band and X-band, although often miniaturized using more up-to-date technology as compared to larger satellites. Tiny satellites such as nanosats and small microsats may lack the power supply or mass for large conventional radio transponders, and various miniaturized or innovative communications systems have been proposed, such a laser receivers, antenna arrays and satellite to satellite communication networks. Few of these have been demonstrated in practice.

Electronics need to be rigorously tested and modified to be «space hardened» or resistant to the outer space environment (vacuum, microgravity, thermal extremes, and radiation exposure). Miniaturized satellites allow for the opportunity to test new hardware with reduced expense in testing. Furthermore, since the overall cost risk in the mission is much lower, more up-to-date but less space-proven technology can be incorporated into micro and nanosats than can be used in much larger, more expensive missions with less appetite for risk.

 

References

  1. de Tristancho, Joshua; Gutierrez, Jordi (2010). «Implementation of a femto-satellite and a mini-launcher». Universitat Politecnica de Catalunya: 3. Retrieved 2012-12-12.
  2. Lindsey, Clark (2012-12-19). «DARPA developing microsat constellation orbited with air-launch system». NewSpace Watch. Retrieved 2012-12-22. (subscription required (help)).
  3. Messier, Doug (2013-04-04). «Garvey Nanosat Launcher Selected for NASA SBIR Funding». Parabolic Arc. Retrieved 2013-04-05.
  4. Norris, Guy (2012-05-21). «Boeing Unveils Air-Launched Space-Access Concept». Aviation Week. Retrieved 2012-05-23.
  5. Small Is Beautiful: US Military Explores Use of Microsatellites». Defense Industry Daily. 2011-06-30. Retrieved 2012-12-12.
  6. Virgin Galactic relaunches its smallsat launch business». NewSpace Journal. 2012-07-12. Retrieved 2012-07-11.
  7. Virgin Galactic unveils LauncherOne name!, Rob Coppinger, Flightglobal Hyperbola, December 9, 2008
  8. Werner, Debra (2013-08-12). «Small Satellites & Small Launchers | Rocket Builders Scramble To Capture Growing Microsat Market». Space News. Retrieved 2013-11-01.

 

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