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Overview

PACE is a 2 Unit CubeSat and has a size of 112mm x 112mm x 243mm at a total mass of less than 2 kilograms. The outside is equipped with solar cells, a hard-wire interface port, antennas, sun sensors and mechanisms. Inside the spacecraft are the electronic boards and the actuators for attitude control.

 Spacecraft Description

The structure and mechanism (SMS) elements are milled from Al-6061 aluminum alloy to provide a rigid but light-weight frame. The main structure is completely demountable to facilitate the spacecraft assembly. A secondary structure is integrated to mount the attitude actuators.

High-efficient space solar cells are used as energy supply. In order to assure continues supply of electrical energy even in the times when the satellite is in the shadow of the earth, the electrical power system (EPS) includes lithium-ion batteries for energy storage. The on-board power is regulated and available at 3.3 and 5 Volt. 

For the reception of commands and the downlink of data, the communication system (COM) of PACE transmits on an amateur radio frequency in the 70cm band. The commands and data are sent as Ax.25 packets and are modulated in FSK. 

An on-board command and data handling system (CDHS) runs the software for interpretation of mission commands and event handling. It uses an 8051 microprocessor to run the flight software and nonvolatile mass memory for data storage.

Finally, the attitude determination and control system (ADCS) makes up the main part of the satellite. It is composed of several items. A powerful microprocessor runs the software for attitude determination and control. It can be reprogrammed in-flight via the CDHS. Four digital sun sensors, a three-axis magnetometer, as well as three body-axes aligned gyroscopes are used for attitude sensing. A momentum wheel and magnetic coils are available for actuation, i.e. to control the attitude of the satellite.

Structure and Mechanisms

   Material

   Mechanisms

 

Al6061, anodized

Kill switch, RBF, antenna deployment

Power

   Solar cells  

   Nominal solar input

   Battery type

   Battery pack capacity

   Voltage levels

 

20x TJ GaAs

2 W

Lithium-Ion

3.6 Ah

3.3 V, 5 V, battery output (nom. 3.7 V)

Communication

   Type

   Packet modulation

   Packet protocol

   Beacon modulation

   Beacon protocol

   RF max output power

   Frequency

   Bandwidth

   Antenna type

 

Non-coherent, half-duplex, 20K00F1D

FSK 1200 baud

Ax.25

OOK 15 WPM

Morse code

1 W

437.xxx MHz (up/down)

20 kHz

Half-wave dipole

Attitude

   Magnetometer

   Gyroscope

   Digital sun sensor

   Magnetorquer

   Momentum wheel

 

1.0 V/gauss, 1.9 gauss

12.5 mV/deg/sec, 150 deg/sec

1 deg, 60 deg

0.2 Amp-m2

0.002 N-m-sec at 2000 rpm

Command and Data

   Processor

   Memory

 

2x 8051 microcontroller

16 Mbyte Flash

 

 

 

 

 

 

 

 

 

 

 

 

 

 


(c) 2010 PACELAB, NCKU