Mars Cube One
Communications relay test|
|Spacecraft type||6U CubeSat|
|Launch mass||13.5 kg (30 lb) each|
|Start of mission|
|Launch date||5 May 2018, 11:05 UTC|
|Rocket||Atlas V 401|
|Launch site||Vandenberg Air Force Base SLC-3E|
|Contractor||United Launch Alliance|
Mars Cube One (or MarCO) is a Mars flyby mission consisting of two nanospacecraft, of the 6U CubeSat format, that was launched on 5 May 2018 alongside NASA's InSight Mars lander mission. Mars Cube One is intended to be a test of new miniaturized communications and navigation technologies. Should the two CubeSats make it all the way to Mars, they will be able to provide a real-time communications link to Earth for InSight during its entry, descent, and landing when InSight will be out of sight from the Earth. Mars Cube One is the first spacecraft built to the CubeSat form to operate beyond Earth orbit; besides telecommunications, they will also test CubeSats' endurance in deep space.
The InSight lander will retransmit its telemetry data soon after landing. Therefore, the MarCO is not critical for the Insight mission, but it will demonstrate the new relay system and technology for future use in missions to other Solar System bodies.
Mars Cube One is the first spacecraft built to the CubeSat form to operate beyond Earth orbit for a deep space mission. CubeSats are made of small components that are desirable for multiple reasons, including low cost of construction, quick development, simple systems, and ease of deployment to low Earth orbit. They have been used for many research purposes, including: biological endeavors, mapping missions, etc. CubeSat technology was developed by California Polytechnic University and Stanford University, with the purpose of quick and easy projects that would allow students to make use of the technology. They are often packaged as part of the payload for a larger mission, making them even more cost effective.
The two Mars Cube One spacecraft are identical and officially called MarCO-A and MarCO-B and were launched together for redundancy; however, they were nicknamed by JPL engineers as WALL-E and Eva in reference to the main characters in the animated film WALL-E.
The launch of Mars Cube One was managed by NASA's Launch Services Program. The launch was originally scheduled for 4 March 2016 on an Atlas V 401, but the mission was postponed to 5 May 2018 after a major test failure of an InSight scientific instrument. The Atlas V rocket launched the spacecraft together with InSight, then the two MarCO separated soon after launch to fly their own trajectory to Mars in order to test CubeSats' endurance and navigation in deep space.
The primary mission of MarCO is to test new miniaturized communication and navigation technologies. Should the two cubesats make it to Mars, they are able to provide real-time communication relay while the InSight lander is in the entry, descent, landing phase.
The MarCO spacecraft are flying as a pair for redundancy. While there are a large number of CubeSats around Earth, Mars Cube One is the first CubeSat mission to go beyond Earth orbit. This will allow for collection of unique data outside of the Earth's atmosphere and orbit. In addition to serving as communications relays, they will also test the CubeSat platform's endurance and navigation capabilities in deep space. Instead of waiting several hours for the information to relay back to Earth directly from the InSight lander, MarCO will relay EDL-critical data much sooner . Without the MarCO CubeSats, InSight would relay the flight information to Mars Reconnaissance Orbiter (MRO) which does not transmit information as quickly. Seeing the already-present difficulty in communicating with ground control during especially risky situations, various teams set out to revise the way in which data is relayed back to Earth. Previous missions would send data directly to Earth after landing, or to nearby orbiters, which would then relay the information. Future missions may no longer be able to rely on these methods, CubeSats may be able to improve data relay in real time, as well as reduce the overall mission cost.
Design and components
The design includes two communication-relay CubeSats, built by NASA's Jet Propulsion Laboratory, which are of the 6U specification (10×20×30 cm). A limiting factor to the development of CubeSats is that all necessary components must fit within the frame of the satellite. It must contain the antenna, avionics to control the satellite, a propulsion system, power, and payload.
On board the two CubeSats will be an ultra-high frequency (UHF) antenna which is circularly polarized. The EDL information from InSight will travel through the UHF band at 8 kbit/s to the CubeSats, and will be simultaneously retransmitted at an X band frequency at 8 kbit/s to Earth. MarCO will use a deployable solar panel for power, but because of the limitations in solar panel efficiency, the power for the X-band frequency can only be about 5 watts.
In order for the CubeSats to be able to relay information, they need to have a high gain antenna (HGA) which is reliable, meets the mass specs, has low complexity, and is affordable to build. A high gain antenna is one that has a focused, narrow radiowave beam width (directional antenna). Three possible types of antennas were assessed: a standard microstrip patch antenna, a reflectarray, and a mesh reflector. With the small, flat, size required for the CubeSats, the reflectarray antenna type met all of the mission needs. The components of a reflectarray HGA are three folded panels, a root hinge which connects the wings to the body of the CubeSat, four wing hinges, and a burn wire release mechanism. The antenna panels must be able to withstand a varying degree of temperature changes throughout the mission as well as vibrations throughout deployment.
The propulsion system features eight cold gas thrusters which control the trajectory, and a reaction control system to adjust their attitude (orientation). On the way to the correct transmission destination, the propulsion system will make five small corrections to ensure the two small spacecraft are on the correct trajectory. A small change in trajectory early on in the mission's deployment will change the path of an object more effectively and with less fuel than if the course corrections were made upon arrival to Mars. The smaller corrections not only save fuel but also the space which the fuel would have taken up, thus conserving volume for other important components inside the spacecraft.
|Wikinews has related news: NASA's InSight lander and MarCO craft launch in new mission to Mars|
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