ESTCube-1

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ESTCube-1
ESTCube-1 illustration.jpg
ESTCube-1 illustration
Mission type Technology
Operator University of Tartu
COSPAR ID 2013-021C
SATCAT № 39161
Website http://www.estcube.eu/en/home
Mission duration 12 months
Spacecraft properties
Launch mass 1.048 kilograms (2.31 lb)
Start of mission
Launch date 7 May 2013, 02:06:31 (2013-05-07UTC02:06:31Z) UTC
Rocket Vega
Launch site Kourou ELA-1
End of mission
Deactivated 17 Feb 2015, 10:27:00 (2015-02-17UTC10:27Z) UTC[1]
Decay date 2038*estimated
Orbital parameters
Reference system Geocentric
Regime Low Earth
Inclination 98.129 degrees
Period 98.03 minutes

ESTCube-1 is the first Estonian satellite and first satellite in the world with an electric solar wind sail (e-sail). Developed as part of the Estonian Student Satellite Program, it was launched on 7 May 2013 aboard a Vega carrier rocket[2] and successfully deployed into orbit.[3] Student Satellite is an educational project in which university and high school students can participate.[4][5] 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.[6][7]

Scientific purpose

File:The first image of the Earth, taken by ESTCube-1 nanosatellite..png
The first image of Earth taken by ESTCube-1 on May 15, 2013.[3]
File:ESTCube-1 E-sail experiment.jpg
ESTCube-1 E-sail experiment
File:The structure of cubesat ESTCube-1 eng.jpg
The structure illustration of cubesat ESTCube-1
File:ESTCube-1 struktuur koos plaatidega.jpg
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 the ESTCube-1 flight, 10 meters of 20–50 micrometer thick E-Sail wire, sometimes referred to as "Heytether," were deployed from the satellite. The deployment of the Heytether is detected by a decrease of the satellite's rotation speed or an onboard camera.[8]

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 nanotechnology 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 plasma on 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 small satellites from 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 acquire images of Earth and to monitor deployment of the Heytether.

Orbit

To complete the scientific experiment and communicate with the satellite on several occasions the orbit chosen was a sun–synchronous circular orbit at an altitude of 670 kilometers. ESTCube-1 was launched into orbit by Arianespace, using a Vega rocket which lifted off from ELA-1 at Kourou at 02:06:31 UTC on 7 May 2013. The satellite was placed into orbit and communication successfully established,[9] with the first photo of the Earth taken on May 15 and transmitted to the ground on the amateur radio band.[3]

Lifespan of the satellite

The plan, beginning with the 7 May 2013 launch, included the following steps:

  • Half an hour after the satellite's deployment from the start capsule, the satellite's antennas were deployed and radio transmitter and important subsystems were switched on.
  • During first 48 hours after the deployment, the satellite sent only safe-mode CW beacon signals
  • The first weeks were used to test the satellite and set it to work at full capacity.
  • Orientation of the satellite so the on-board camera was facing Earth to acquire images of Estonia.
  • Rotation of the satellite on its longitudinal axis with a speed of 1 revolution per second.
  • E-Sail element deployment from the satellite by centrifugal force and confirmation of the deployment via the on-board camera.
  • Activation of the electron emitter and the loading of the E-Sail
  • Measurement of the E-Sail Lorentz force via satellite's revolutions per second
  • If possible, attempt to use the negatively charged E-Sail to take the satellite off orbit and reenter the Earth's atmosphere.

The last morse code transmission was transmitted on 17 February 2015 as the batteries became exhausted. The plan to test a solar sail the satellite carried, failed since the sail cable unwinding mechanics did not survive the rocket takeoff vibration.[10]

Design

Measurements and weight

During the development of the Estonian satellite mission it was decided to make a 1U CubeSat. 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. Mass is also set in CubeSat standard, the highest possible mass for 1U CubeSat is 1300 grams.

Communications

Communication from the satellite is made at two International Amateur Radio Unions registered frequencies

  • 437.250 MHz
  • 437.505 MHz[11]

Periodic but very slow communication is made by using 18 WPM telegraphy signal on a frequency of 437.250 MHz. At that frequency, the most important satellite parameters are returned every 3 to 10 minutes. For fast connections FSK-modulation radio signals on a frequency of 437.505 MHz with a 9600 baud connection speed and AX.25 packet standard is used. The relatively slow connection speeds result from the use of amateur radio frequencies which limits the bandwidth to 25 kilohertz. The fast connection is used only when the satellite has been given a specific order. Both telegraphy and packet telemetry protocols of ESTCube-1 are published on project webpage.[12][13]

Commands sent to the satellite use the 145 MHz (2 meter) amateur band.

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 by the students of Tartu University under the supervision of the company CGI Group.

Financing and costs

File:ESTCube-1 esitlus.jpg
ESTCube-1 presentation in January 2013.

The least expensive satellite launch is offered by the European Space Agency. Because Estonia is an associated member of ESA, most of the launch expenses (about 70,000 euros) were covered by the Estonian member fee for educational expenses. With the launch, total expenses for the project were approximately 100,000 euros.

Results

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See also

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ ESA: Launch schedule
  3. ↑ 3.0 3.1 3.2 Southgate Radio Amateur News, First picture from ESTCube-1 ham radio CubeSat, May 22, 2013 (accessed Aug. 16 2013)
  4. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  6. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Matteo Emanuelli, Estonian Cubesat on a Collision Course with Iridium-Cosmos Debris, August 1, 2013, Space Safety News (accessed Aug. 16 2013)
  10. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ Lua error in package.lua at line 80: module 'strict' not found.

External links

Videos
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