Cube Sats

Hello everyone!

Cubesats are a modern, refined and highly miniaturized version of the bulky satellites that we currently employ into Earth orbit for all purposes such as communications and scientific experiments. Cubesats allow a number of distinct advantages over conventional satellites and are gaining popularity as a means of accomplishing targeted individual space missions

.cubesatkit_1u-revd-skeleton

Cubesats are typically small cubical units that contain standard communication equipment, attitude control and scientific equipment housed within a small cubic aluminium alloy housing with sides roughly about 10 centimeters each. This allows for about a liter of useful volume that is quite enough to fit in all the required material for controlled spaceflight.

Satellites are typically classified on the basis of their weight

  • Minisatellites: 100-500kg
  • Microsatellites:10-100kg
  • Nanosatellites:1-10kg
  • Picosatellites:0.1-10kg
  • Femtosatellites:0.01-0.1kg

Cubesats typically come under the picosatellite category as their weight is not more than 2 kg in most instances.

cubesat_pic

The biggest advantage of such a unique construction is the major reduction in cost of the payload owing to the reduced weight and dimensions of the spacecraft. This provides the added benefits of allowing people to design and manufacture satellites for riskier missions as a failure of the spacecraft will be marginal as compared to the failure of a bigger spacecraft. This also allows satellite designs for individual space missions that would not justify the costs of designing, manufacturing and deploying a larger spacecraft.

Another benefit of the smaller payload is that it allows launching multiple Cubesats on the same launch. In fact, the DIY nature of the Cubesats have allowed a greater number of countries with no formal space programs to experience satellite launches and related space technology. Cubesats were in fact, the very first indigenuously manufactured satellites for Switzerland and Denmark.

Cubesats have also allowed academic institutions and enthusiasts to enjoy and experience the thrill of building their own spacecraft. The concept of Cubesats was pioneered by California Polytechnic State University and Stanford University around 1999 and a majority of the launches since then, were for academic purposes.

How do you deploy Cubesats? Well, Cubesats can be deployed by releasing them from their mounts on a launch vehicle when a specific trajectory is achieved. Cubesats have also been deployed from the International Space Station from the NanoRacks CubeSat Deployer (NRCSD). Cubesats have  also been deployed by hand during a spacewalk on the International Space Station!

nrcsd
NRCSD deploying Cube Sats from the ISS

The major components of any Cubesat are the Housing, Computing and data storage equipment, Propulsion Systems, Attitude control, Communications equipment and a thermal management system.

cubesat-assembly

The Housing is made up of an aluminium alloy that is similar to the material of the mounting equipment on the spacecraft to prevent jamming during deployment due to cold welding in space. The Computing equipment has a primary computer that handles tasks such as attitude control, image processing and power management systems along with a secondary computer that mainly handles raw data processing and preventing overloading the main computer.

Attitude control is a major component of a Cubesat and is one of the major weight components. It is generally achieved by employing star trackers and sun sensors combined with reaction wheels or thrusters to maintain the desired attitude of the satellite. Propulsion systems are used for long term missions as they form the bulk of the satellite, taking up the limited available space. The Cubesat can use electric propulsion, solar sails or chemical propulsion. The biggest challenge for deploying a propulsion system apart from space constraints is to ensure that the onboard equipment is not  damaged in any manner.

Image result for cubesat electronics

Due to the limited power supply that the Cubesat can carry (About 2W) and the difficulty in maintaining attitude, the telecommunications equipment is generally omidirectional and with a lower range with communication in the form of UHF and VHF transmission bands.

Being in space, the Cubesats undergo a drastic temperature variation due to the Sun’s thermal radiation and low heat dissipation rates. To counter this, Cubesats generally have multiple insulating layers over the sensitive components. Temperature sensors on the Cubesat can be coupled to the propulsion systems to alter the orientation of the spacecraft to allow even heating or cooling.

A very significant launch event will be happening in 2018, with the NASA InSight Lander to Mars, which will be deploying two cubesats midway on its trajectory to Mars. The two Cubesats (called MarCo Cube Sats) will fly by Mars at the exact time of the actual Lander and will provide real time telemetry of the descent by acting as relay satellites along with the Mars Reconnaissance Orbiter. This will be the first time, that CubeSats would be deployed for such a purpose beyond the Earth’s Sphere of Influence.

Well, I would like to end this post here. Hope this was informative and interesting!

Until Next Time! 🙂

References and Further Reading:

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