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ESTCube-1

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Template:Infobox Spacecraft ESTCube-1 is a satellite created by The Estonian Student Satellite Program that is scheduled to be launched to orbit in the second half of 2013. Student Satellite is an educational project that university and high school students can participate in.[1][2] The CubeSat standard for nanosatellites was followed during the engineering of ESTCube-1, resulting in a 10x10x11.35 cm cube, with a volume of 1 liter and a mass of 1.048 kg.[3]

Measurements and weight

By standard 1 unit (1U) CubeSat base side length must be 100.0±0.1 millimeters and satellite height must be 113.5±0.1 mm. According to the CubeSat standard there are three different sized CubeSat's corresponding to size 1U, 2U and 3U. Base side lengths are the same but height is 2 to 3 times bigger than 1U CubeSats. Mass is also set in CubeSat standard, the highest possible mass for 1U CubeSat is 1300 grams, 2U CubeSat 2600 grams and 3U CubeSat 4000 grams. During the development of the Estonian satellite mission it was decided to make a 1U CubeSat.

Scientific purpose

ESTCube-1 E-sail experiment
The structure illustration of cubesat ESTCube-1
ESTCube-1 structure

While emphasis was placed on educating students during creation of ESTCube-1, it does have a scientific purpose. On board the satellite is an electric solar wind sail (e-sail) which was invented by Finnish scientist Pekka Janhunen. During an ESTCube-1 flight, 10 meters of 20-50 micrometer thick e-sail wire, sometimes referred to as "Heytether," is deployed from the satellite. The deployment of the Heytether is detected by a decrease of the satellite's rotation speed or an on-board camera.[4]

To control the e-sail element's interaction with both the plasma surrounding the earth and the effect it has on the spacecraft's spinning speed, two nanotechnologic electron emitters/guns are on board. The electron emitters are connected to the e-sail element which it loads positively to 500 volts by shooting out electrons. The positive ions in the plasma push the e-sail element and influence the satellite's rotation speed. The effect of the e-sail is measured by the change in said rotation speed.

After the measurements on the e-sail effect are completed, the Heytether is used as a plasma-brake by loading its ionosphere opposite to the plasma's ionosphere. This demonstrates a possibility for returning little satellites down form the orbit. A color CMOS camera is also on board that is capable of making RAW-format pictures with VGA-resolution. This camera is used to take a picture of Earth and the successfully deployed Heytether.

Orbit

To complete the scientific experiment and communicate with the satellite on several occasions the best orbit is sun–synchronous circular orbit on the altitude of 670 kilometers. ESTCube-1 will be sent to orbit by the European Space Agency's rocket Vega in spring of 2013.

Lifespan of the satellite

  • Start in spring of 2013.
  • Half an hour after the satellites deployment from the start capsule satellites antennas will be opened and radio transmitter and important subsystems will be switched on.
  • First days or weeks will be used to test the satellite and set it to work on full capacity.
  • Orienting the satellite so the on-board camera will be faced to earth and with good luck trying to take a picture of Estonia.
  • Rotating the satellite on an axis with a speed of 1 revolution per second.
  • E-sail element deployment from the satellite by a centrifugal force and confirming the deployment via the on-board camera.
  • Activating the electron emitter and loading the e-sail
  • Measuring the e-sails and Lorentz force by satellites revolutions per second
  • If possible using the negatively charged e-sail to take the satellite off orbit and burn it in the earths atmosphere.

If everything goes perfect the mission can be completed within a few weeks to a month.

Communicating with the satellite

Communication with the satellite is held by two International Amateur Radio Unions three registered frequencies

  • 437.250 MHz
  • 437.505 MHz[5]

Periodic but very slow communication is done on a telegraphic signal on a frequency of 437.250 MHz. With that way the most important satellite parameters are transmitted every 3 to 5 minutes. For fast connections FSK-modulation radio signal on a frequency of 437.505 MHz with a 9600 baud connection speed and AX.25 standard is used. Somewhat slow connection speed is caused by the usage of amateur radio frequencies which allow a maximum of 25 kiloherz bandwidth. Besides FSK-modulation transmitter there are also GFSK-, MSK-, and GMSK-modulation signal transmitters. Using the GFSK-modulation maximum possible connection speed is 19,200 bits per second. Fast connection is used only when the satellite has been given a specific order.

For giving orders to satellite amateur signal 145 MHz is used.

Software

ESTCube-1 microcontrollers use the following operating systems.

  • FreeRTOS on the satellite's Command and Data Handling System and camera module.
  • TinyOS on the satellite's communication module. (Typically used with devices running on low power)

Mission Control System is currently being developed with the company CGI Group.

Financing and costs

Cheapest possibility to send a satellite onto orbit is offered by European Space Agency. Because Estonia is an associated member of ESA most of the launch expenses (about 70,000 euros) will be covered from Estonian member fee for educational expenses. With the launch total expenses for the project are approximately 100,000 euros.

See also

References

  1. ^ "The two primary payloads for Vega's second launch are readied at the Spaceport". Arianespace. March 14, 2013. Retrieved March 25, 2013.
  2. ^ "Arianespace Awaits...Vega Tops Off While Sats Prep For Vegies (Launch)". satnews. March 14, 2013. Retrieved March 25, 2013.
  3. ^ "Estonia's student cubesat satellite is ready for the next Vega launch". Arianespace. Retrieved March 25, 2013.
  4. ^ "Proba-V's fellow passenger" (PDF). European Space Agency. February 2013. p. 17. Retrieved March 25, 2013.
  5. ^ "ESTCube-1". International Amateur Radio Union. 15 Mar 2013. Retrieved March 25, 2013.
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