Command & Data Handling¶
The Command and Data Handling (C&DH) system performs two major functions: (1) It receives, validates, decodes, and distributes commands to other spacecraft systems and gathers, processes; (2) and formats spacecrafts housekeeping and mission data for downlink or use by an onboard computer. This equipment often includes additional functions, such as spacecraft timekeeping, computer health monitoring (watchdog) and security interfaces.
The C&DH subsystem is the “brain” of the whole spacecarft. It consists of an Onboard Computer, OBC, which controls the operation of the satellite. The OBC has software installed that manages the programs written to handle various tasks; for example, a program whose function is to create a telemetry stream about the status of the payload and then encode the stream. The primary component of the OBC is the microcontroller.
The objective of the C&DH subsystem is to provide the spacecraft with operation sequences to various subsystems. Because of the size restrictions of the typicall satellites, the C&DH subsystem needs to be efficient, small, lightweight, and easy to integrate with all of the other subsystems. The ideal C&DH system is one which has been proven on another spacecraft and which requires no modification for the mission under development. However, new missions are usually supported by systems which evolve from older designs.
Table 2 summarizes a list of different space missions in terms of S/C mass. It includes de misions name and objetives and the spacecraft size, mass, power consumption, and the C&DH equipment configuration.
| Satellite | Mission | Size | Mass | Power | C&DH Subsystem |
|---|---|---|---|---|---|
| MCubed-2 / COVE | Imaging / Optical | 10 cm x 10 cm x 10 cm (1U) | ~ 1 kg | 1.2 W of average power, 4.7 W of peak power | Stamp9G20 microcontroller (OBC), 400 MHz ARM9 core, 54 MB SDRAM, 128 MB NAND flash |
| OUFTI-1 | Tech / Navigation / Conmmunication | 10 cm x 10 cm x 10 cm (1U) | ~ 1 kg | 2.2 W | Pumpkin FM430 microcontroller (OBC), two 2GB SD cards for data storage |
| StudSat-1 | Imaging / Optical | 10 cm x 10 cm x 13.5 cm (1U) | 1.3 kg | 3.2 W | Centralized 32-bit Atmel ARM based AVR32 UC3A0512 microcontroller (OBC), 512 kB FRAM |
| Galassia | Tech / Navigation / Conmmunication | 10 cm x 10 cm x 20 cm | 2 kg | 2 W | 16 bit DSPIC33 Microcontroller (OBC), ARM7 Processor |
| Raiko | Imaging / Optical | 10 cm x 10 cm x 23 cm (2U) | 2.66 kg | 3 W (Paddles closed), 5.9 W (Paddles open) | A Main Processor Unit (MPU), Power Control Unit (PCU), Flash memory |
| GOMX-1 | Imaging / Optical | 10 cm x 10 cm x 20 cm (2U) | 2.66 kg | 3.5 W | NanoMind A712 Microcontroller (OBC), 2 GB of data storage |
| QBITO | Space Science | 10 cm x 10 cm x 23 cm (2U) | 2.66 kg | Electronic Systems CubeComputer V3 (OBC) | |
| PicSat | Space Science | 10 cm x 10 cm x 30 cm (3U) | 3.5 kg | ISIS ARM9 Processor (OBC), two 3 GB SD cards | |
| Aalto-1 | Tech / Navigation / Conmmunication | 10 cm x 10 cm x 34 cm (3U) | ~ 4 kg | 4.8 W | AT91RM9200 ARM 9 Processor (OBC), External RAM, EEPROM, DataFLash, NAND Flash and microSD for data storage, two 32 MB SDRAM modules |
| INSPIRE | Tech / Navigation / Conmmunication | 10 cm x 10 cm x 30 cm (3U) | ~ 4 kg | 20 W | Pumpkin MSP430 processor (OBC), Two 2GB SD cards for data storage |
| VELOX-1 NSat | Imaging / Optical | 10 cm x 10 cm x 34 cm (3U) | 4.28 kg | 28.8 W | Main board with 100 MHz 8051 MCU (OBC), 2 GB SD cards for data storage, 32 MB RAM |
| OPS-SAT | Tech / Navigation / Conmmunication | 10 cm x 10 cm x 30 cm (3U) | 5.4 kg | GomSpace Nanomind A712D | |
| SPROUT | Imaging / Optical | 21.3 cm x 21.3 cm x 21 cm | ~ 7.1 kg | 2 C&DH (1 for the Engineering misión and another for the outreach mision) | |
| ASTERIA | Space Science | 11.6 cm x 23.9 cm x 36.5 cm (6U) | 10.16 kg | 48 W | Spaceflight Industries CORTEX 160 Flight Computer, Xilinx Virtex 4FX / PowerPC405, 14.5 GB for data storage |
| MasCO | Space Science | 11.8 cm x 24.3 cm x 36.6 cm (6U) | ~ 12 kg | 35 W | AstroDev MSP430F2618 Microcontroller (OBC), 128 kB flash memory, 8 kB RAM |
| IceCube | Space Science | 11.8 cm x 24.3 cm x 36.6 cm (6U) | ~ 14 kg | 120 W | Proton P400K-SGMII-2-PCI104S-SD Space Computer (OBC), Freescale advanced 45 nm dual-core microprocessor |
| BUAA-Sat | Imaging / Optical | 30 cm x 30 cm x 50 cm | ~ 30 kg | 11 - 15.5 W | 32 bits ARM RISC Processors, PC2294 of 60 MHz, SRAM 2 MB |