maroc-tubsat and lapan tubsat - fred sigernesfred.unis.no/agf218/lecture4_2_maroc_lapan.pdf ·...

Satellite and Sounding Rocket Construction

The University Courses on Svalbard, Longyearbyen August/September 2006 MAROC- and LAPAN-TUBSAT

MAROC-TUBSATand

LAPAN TUBSAT



• MAROC-TUBSAT Mission Goals– Test of the advanced attitude control system– teach the Morocians in microsatellite construction, operations,

space condition requirements and orbital mechanics

• Satellite Bus• Operation

• Payload• Operation

Royal Institute for EarthObservation RABAT

Technical University of Berlin

MAROC-TUBSAT Project



MAROC-TUBSAT Split View

• Mass: 47 kg• Cube: 32×34×36.2 cm



MAROC-TUBSAT Payload Module (Rutherford)

• One CCD-sensors containing 770x576 pixel and a pixel size of 32 μm (incl. Near infrared)– focal length 72 mm– fov 8°– nominal integration time 28 ms– only photo

• S-Band transmitter– BPSK modulation– 2 W RF output– digital pictures or telemetry with 128 kbaud



Attitude Control System• Three Wheel/Gyro-Units in

the three body axes– Wheel with integrated WDE

(built by TUB)– Fibre optic gyro µFORS-6

(built by LITEF)– Gyro is connected to integrated

WDE via serial communication interface

Operating modes Current control Angular velocity controlSpeed control Angle control Torque control



Ground Segment International• Norway

– University of Svalbard (TTC)– SvalSat (Payload)

• South Africa– University of Stellenbosch– Overberg Test Range

Telemetry/Telecommand-

Station

Transceiver UnitVHF/UHF-Band

Yagi-Antenna

Telemetry/Telecommand1200 Baud

2.4 m Maroco/Rabat4 m SA/Stellenbosch

4 m SA/Overberg7 m Norway/Tromsoe

Digital Pictures125 kBaud

Bit-/Bytesynchronisation

Picture Storage

DigitalReceiver Unit

S-Band

Cooperated Satellite Control Center

Videodata are sendto Berlin via mail or

internetcould be

controlled fromBerlin via internet,

but normalautonomous



DLR- versus MAROC-TUBSAT



• Star Sensor is used occasionally (once per Day) to close the Outer Loop (Momentum Bias, Drift Rate less than 1° per Day, no man in the Loop)

• Can work worldwide - autonomously

• Payload Camera is used to close the Outer Loop (Man in the Loop, Zero Momentum Bias)

• Needs S-Band and TTC-station near observation area

DLR-TUBSAT

MAROC-TUBSAT



Attitude Control System - Inertial• CCD Star Sensor

– developed by TU Berlin

• Operating Mode– Momentum Bias Mode– Momentum axis perpendicular to

orbital plane– Momentum axis direction is

known by 0.2°



Attitude Control Operation Step 1.Sleep mode:

Satellite rotates around it’s Z-Axis with 1°/sec, momentum bias vector stands perpendicular to the orbital plane

2.First Attitude Acquisition: • Momentum bias vector is split up between Z and X-Axes

(primary to X). This defines the East/West position of image centre

• satellite rotates with 1°/sec around X; Y control circuit is nutation damping (30 min)



3.Second Attitude Acquisition:• If the satellite reaches its target solar

cell current (rising or falling flank) the RW reduce the rotation to 0.5°/sec (RPM mode)

• After one half of the nutation period the RW reduce the rotation to 0°/sec

• Angle step back to the target position by using RW-Gyro pair

• Fine adjustment every 5 sec until the time for first picture is reached.• Taking of 24 or 28 pictures and send the data down or taking one

picture and store it.• After completing the picture sequence the satellite goes back to sleep

mode.



TUBSAT Attitude Control

North pole

-Y

1

2

3

Region to be imaged

Ground track +Z

Sun

equatorGround track

Region to be imaged

1

2

3

+Z

trajectory

CROSS TRACK OFF-NADIR TARGET LOCKING

INTERACTIVE AND AUTONOMOUS MODES



Operations• Satellite is rotating around momentum bias axis (hibernation mode)• Stabilize satellite rotation by rate command with wheel/gyro-units

(10 min before target)• Acquisition with sun vector information to point target and stabilize

(1 min before target)• Take picture of target• Store picture or send it down and make a new picture (max. 25

overlapping pictures)• Possibility of stereoscopic pictures• Switch off three wheel/gyro-units• Go back to momentum bias mode mode



Flight Results: Pictures



Long Time Monitoring

Interval of Events:

- Hourly, e.g. Weather (NOAA)

- Daily, e.g. Ice Movement, Vegetation This is the Typical Application for MAROC-TUBSAT

- Weekly or Monthly, e.g. City Expansion (Landsat)



An Example: Ice Monitoring for Icesail Expedition(Arved Fuchs)



Detection of Ice free Shipping Lanes:

Gulf of Finland 20 March 2003Gulf of Finland 27 March 2003



-3D Bilaufnahme

-2 Bilder a 30 sec

-280 km stereo basis



Disadvantages of MAROC TUBSAT• Target position must be known exactly• Too less storage capacity• To small focal lenght• panchromatic

Advantages of MAROC TUBSAT• Autonomous operation worldwide• Do not need S-Band and TTC station in contact range

of the target• Hibernation mode is easier to control



The near Future: LAPAN-TUBSAT• Similar to MAROC-TUBSAT with some Improvements:

– Color TV (3 Chip) Camera– Focussing on board– 1 m Focal Length– Star Sensor (CMOS)– 5 Battery Cells– Modified Shape

• 44 x 44 x 25 cm (instead of 32 x 32 x 32 cm)

• Launch is planned for October 2006



LAPAN-TUBSAT• Cooperation of TU-Berlin and LAPAN Indonesia

• Technical Part– Building of a microsatellite for earth observation with 6 m GSD– Sun Synchronous Orbit, Launch with PSLV (India)– Costs: 1 Million Euro

• Educational Part– Teaching of 10 engineers from LAPAN in Satellite design, choosing of

Components, test procedures, launch pad operations and satelliteoperation



Final Goals



Agriculture Observation



Ship monitoring – securing of fishingfields



Disaster Monitoring

maroc-tubsat and lapan tubsat - fred sigernesfred.unis.no/agf218/lecture4_2_maroc_lapan.pdf ·...

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