Astro-und Feinwerktechnik

Adlershof GmbHACSTest Stand

Testing the attitude control system(ACS) for a micro satellite is one ofthe most complex steps in the verifi-cation process. Software-in-the-loopsimulations (SILS) and hard-ware-in-the-loop simulations (HILS) have longbeen the established test methods,but the ideal solution is a genuineend-to-end test on a test standdesigned for that purpose.Based on the experience gainedfrom various satellite projects, Astro-und Feinwerktechnik AdlershofGmbH has developed such a facility.

ACSTest Stand

•free rotation about the verticalaxis, 20° rotation about the twohorizontal axes

•8 µm to 10 µm air bearing gapfor very low disturbance torques

•safety mechanism for test standpressure loss or power failure

•moment of inertia from 2 kgm2 to30 kgm2

•test object weight up to 130 kg(depends on the moment of iner-tia)

•integrated electronic center-of-gravity calibration (via WLAN)

•power source and distribution(400 Wh minimum, typical volt-age available at various DC/DCoutputs)

•WLAN command interface tosatellite onboard computer

•magnetic field simulation up to210,000 nT in all three axes

•solar simulation with 50,000 luxfrom any position in uppersphere of test stand

With this test stand a completeend-to-end verification of ACSsystems for mini and micro satel-lites can be carried out with greatpointing accuracy, including long-duration testing. This test stand isan ideal extension of software-in-the-loop and hardware-in-the-looptests with regard to the specialdesign and test requirements thatmini and micro satellites inherit.

The key features of our new ACStest stand are as follows:

Magnetic field simulationThe simulation of the Earth’s mag-netic field consists of a Helmholtzcoil system and a controller unit,which produce a maximum field of210,000 nT with a accuracy of 1%.The magnetic field simulation usesNORAD TLE and allows the magnet-ic vector to be generated for anyposition in orbit.

1 Helmholtz coil system for magnetic field simulation2 Sun simulation with adjustment and positioningmechanism

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Electric power supply on the adapter plate,including DC/DC converter box1 rechargeable batteries2 DC/DC converter box3 WLAN command interface4 air-gap monitor and safety-mechanism control

Sun simulationThe test stand uses an HMI lampshining on a 50 cm diameter area onthe air bearing platform to representthe Sun’s illumination in orbit. Thelight from this simulated sun can bedirected to the test object from anyposition in the upper sphere of thetest-stand periphery.

Air Bearing TableBy using a high-precision air bearingand contact-free calibration of the8 µm to 10 µm air gap, the distur-bance forces along all three axes arelow and similar to the magnitude ofmean torque observed by measuringthe changes in the angular momen-tum vector of a satellite in lowerearth orbit. The air bearing table isquipped with a safety mechanismwhich raises the adapter plate onthree pneumatic cylinders when thepressure drops below operatingpressure, power failure occurs, orwhen the compressor is disconnect-ed from the air bearing table.

PlatformTypically, the adapter plate is 80 cmlong; on top there are various inter-faces for connecting the satellite’sACS hardware. The adapter platealso contains the center-of-gravity (CoG) calibration, a powersupply, a power distribution system,and a WLAN command interface.The built-in electronic CoG calibra-tion allows highly accurate adjust-ment. Servo motors adjust a 100 gmass in steps of 0.01 mm in each ofthree axes with the aid of the motorcontroller and the WLAN commandinterface.

Air bearing with safety mechanism arrested1 safety mechanism2 pneumatic cylinders3 air storage tanks

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Astro-und Feinwerktechnik

Adlershof GmbHContact

Erich-Thilo-Straße

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Albert-Einstein-Str.12;12489 Berlin; Germanyphone: +49-30-6392-1000fax: +49-30-6392-1002www.astrofein.com

The Berliner Ring Autobahn (A10)Proceed to the Schönefelder Kreuzinterchange, then take the A113leading north towards SchönefeldAirport. Take the Treptow exit andfollow the B 96a towards Zentrum(the city center). At the Adlershof S-Bahn station (inner-city train lines),turn left on Rudower Chaussee.

The City Freeway (Stadtauto-bahn)Follow the Schönefeld Airportsigns to the Adlershof exit.

Alexanderplatz (in the middle oftown)Take B 96a in the direction ofSchönefeld Airport. At the Adlers-hof S-Bahn station (inner-citytrain lines) turn left on RudowerChaussee.D

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euter,Berlin

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