In the Spotlight: European Space Agency — ESTRACK
Last week I shared some information about the Deep Space Network of NASA. This week we will take a look at how ESA on the other hand stays in touch with satellites and spacecrafts and guarantees communication.
ESA has taken what feels like a bit of a different approach, maybe we can call it historical growth as ESA started with satellites way before sending their own missions out of earth’s gravity pull.
The European Space Agency operates antennas in 7 different locations. The control center is in Darmstadt, Germany (ESOC).
The initial requirement was to provide tracking and communication for satellites and near earth spacecrafts the resulting core stations consist of 13, 15.5 and 15 meter dishes located in
- Kourou (French Guiana)
- Redu (Belgium)
- Santa Maria (Portugal)
- Kiruna (Sweden)
With the first one being Spain and established back in 1975. Twenty three years later in 1998 ESA decided to add deep space capabilities to the communication.
This lead to the first 35m dish which was setup in New Norcia, Australia and today consists of three locations
- New Norcia (Australia)
- Cebreros (Spain)
- Malargüe (Argentina)
On the technology side, there is one big difference between the 35m dish stations and the 13–15m dish stations, the bands in use.
The smaller stations use a mix of S and X Band for communication, the deep space antennas primarily the X Band.
Both Bands used by ESA are located at the lower spectrum of the established satellite frequencies.
In addition, like NASA and other deep space networks, the larger dishes also support the K-Bands.
ESA uses the 2.025GHz to 2.300GHz frequency range of the S-Band, which actually goes from 2 GHz to 4Ghz. Home users might know or at least have read the frequency somewhere on the WiFi part of the home router, as the older standard 802.11b and 802.11g operate at 2.4GHz. The S-Band is pretty immune against weather conditions like rain and fog.
The frequencies 7.145GHz until 8.500GHzbelonging to this band are used by ESA, the full X-Band expands from 8.0 GHz up to 12.0GHz. The X-Band is more affected by weather conditions, and a certain fading due to rain and fog needs to be accounted for.
The K-Bands (K,Ka,Ku) are in the range of 26 to 34 GHz and while the can provide bigger data throughput with smaller dishes there are also the most affected once when it comes to weather.
Although the data rates differ per mission, distance and other factors, generally speaking the bands used can offer between 256 Kbit/s and up to 8 Mbit/s according to ESA’s website. The James Webb Space Telescope on the other hand has been able to push 40 Kbit/s of real time telemetry data according to Wikipedia.
Besides normal tracking and communication, the ground stations can also participate in different experiments, like analyzing the atmosphere of planets by inspecting the signals which have been sent and traversed the atmosphere.
During the Launch and Early Orbit Phase the Estrack service is complemented by commercial partners around the globe like Sweden, Hawaii and Australia to ensure continuous communication with the spacecraft and satellite.
In addition to all the described capabilities,there are 6 DSA stations which can conduct extremely accurate delta-DOR spacecraft tracking campaigns, in order to do this delta- differential one-way range tracking, they are also equipped with GPS receivers and are connected to the ESOC facility directly.
For delta-DOR, the radio signal is received by two individual ground stations which are widely separated at that time. The difference in receiving time is measured and corrected by tracking of radio signals of a quasar within 10 degrees in the same direction.
On a last note to the Ham Radio Operators out there, the X-Band and S-Band can be used by full license holders as well:
- 2.4GHz (13 cm band)
- 3.4GHz (9 cm band)
- 10GHz — 10.5GHz (3 cm band)
Source and Credit: ESA
Special Thanks goes to the Media Relation Office of ESA for clarifying on the K-Band usage and used frequencies
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