Introduction



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Introduction

Telepresence will play a role in future space missions. It is the use of communications to provide a remote projection of human presence, for instance this can be done with robotic rovers remotely piloted by earth based scientists. Robotic rovers require stereo vision using low rate compressed images. Therefore telepresence methods require transmission of integrated video and data. Future manned missions will require integrated voice, data, and video communications systems [7] [8]. Cost minimization requires the establishment of standardized communications techniques that may support these services. The deep space network (DSN) operated by the Jet Propulsion Laboratory (JPL) for NASA consists of an integrated network for communication between space craft and the earth. There are two main segments of this network, the space segment and the earth segment. The space segment will use the Consultative Committee for Space Data Systems (CCSDS) protocol [2] [3] [4]. As the CCSDS is intended for the space segment the characterstics of the channel are long propagation delay, low transmitter power available and random noise. The ground segment may use the emerging standard for broadband communications called Asynchronous Transfer Mode (ATM). ATM is designed for optic fibre high speed networks and so for ATM the channel would be not as long as the space segment and so retransmissions might be possible. Higher transmitter power is also possible. As both standards are designed for different channels there is a need to investigate the interworking of these protocols at the space/ground interface.




Thu Jun 8 12:28:11 BST 1995