satellite communication

Claudemir StenicoClaudemir Stenico

Mr. Miles B. JacobsMr. Miles B. Jacobs

Department ofDepartment of

Electrical EngineeringElectrical Engineering

Employed a simplified data process system Employed a simplified data process system with reduced complexities, low cost with reduced complexities, low cost satellite image reception and analysis satellite image reception and analysis facility.facility.

Weather satellitesWeather satellites

To acquire information and receive To acquire information and receive data data from from weather satellite weather satellite and and to obtain pictures from to obtain pictures from available satellites orbiting South Africa, using:available satellites orbiting South Africa, using:

• FT-847 (Yaesu) FT-847 (Yaesu) • PC (input soundcard)PC (input soundcard)• WXSAT - WXTOIMG (program to process wav files) WXSAT - WXTOIMG (program to process wav files)

AimsAimsAimsAims

144.986 = 1695 MHz (UHF)144.986 = 1695 MHz (UHF)

Polar-orbiters satellites - the IF bandwidth must be wide enough Polar-orbiters satellites - the IF bandwidth must be wide enough to pass the entire signal waveform.to pass the entire signal waveform.

At least 40 - 50KHz At least 40 - 50KHz

FT-847 – 30 KHz (max)FT-847 – 30 KHz (max)

YAESU – FT-847YAESU – FT-847

BandwidthBandwidth

The bandwidth requirement is influenced by The bandwidth requirement is influenced by two factors: the satellite transmitter deviation two factors: the satellite transmitter deviation and the Doppler effect. and the Doppler effect.

NOAA platforms have a signal deviation of NOAA platforms have a signal deviation of about 17 KHz. Adding a Doppler shift of +- about 17 KHz. Adding a Doppler shift of +- 4,5 KHz at the time of closest approach.4,5 KHz at the time of closest approach.

ResultsResults From geostationary satellites From geostationary satellites

central Africa (VIS)central Africa (VIS)

Decoding through the SoftwareDecoding through the Software

WXSATWXSAT

Set up Set up interfaceinterface

1 channel1 channel 2 channels2 channels

Decoding through the SoftwareDecoding through the Software

South America (IR)South America (IR)

Flow signal diagram

Due to the large amount of data, the lowest standard sampling frequency that fulfils the Nyquist criteria the soundcard must have fixed sampling frequency (11025 kHz)

Decoding aspects Decoding aspects

1 channel1 channel 2 channels2 channels

Eastern Africa Eastern Africa (VIS)(VIS)

Wxtoimg

Interface

Decoder Software

Meteosat operations are affected for the two eclipse periods each year when the satellite undergoes an eclipse of the sun by the Earth. The two periods occur at the equinoxes.

During the actual eclipse, certain satellite functions, including earth imaging and all dissemination services are interrupted in order to save power.

Eclipse!!!Eclipse!!!

METEOSAT 7METEOSAT 7

An eclipse of the sun An eclipse of the sun occurs when the satellite occurs when the satellite passes into the conical passes into the conical shadow region of the shadow region of the earth or of the moon.earth or of the moon.

(2004, 20 Oct).(2004, 20 Oct).

Colour enhanced for the GlobeColour enhanced for the Globe

Southern HemisphereSouthern Hemisphere

South AfricaSouth Africa

The futureThe future

During ten years (2000-During ten years (2000-2009), there will be a 2009), there will be a transition of the present transition of the present low-resolution satellite low-resolution satellite service called APT and service called APT and WEFAX to LRPT & WEFAX to LRPT & LRTI, a digital system. LRTI, a digital system.

Everything must still be Everything must still be improved.improved.

Thank you!!Thank you!! Questions??Questions??