A Packet Utilisation Standard (PUS) Model

Transcription

1 A Packet Utilisation Standard (PUS) Model This is a simulation model of the European Space Agency (ESA) Packet Utilisation Standard (PUS) in an operational environment linking a satellite with ground stations. The Packet Utilisation Standard The PUS is linked to the ESA Packet Telemetry and Telecommand Standards, which address the end-to-end transport of telemetry and telecommand data between user applications on the ground and Application Processes onboard the satellite, and the intermediate transfer of these data through the different elements of the ground and space segments. The Packet Utilisation Standard complements the Packet Telemetry and Telecommand Standards by defining the Application-Level interface between ground and space, in order to satisfy the requirements of electrical integration and testing and flight operations. PUS relates to the utilisation of telecommand and telemetry source packets for the purpose of monitoring and remote control of subsystems and payloads. PUS is also used to manage onboard monitoring and control functions for manned missions. PUS packets are used in conjunction with specific Packet Utilisation Standard Services, which correspond to particular monitoring and control functions. Service specifications define: what can be requested of the Service; what can be issued by the Service to notify the user of the success or failure of this request and to report events detected during the execution of the Service activities; what internal activities the Service should perform to process a request or to detect or process events related to the Service PUS packets are used to control and monitor these services via a well-defined set of interactions between the provider of the Service (i.e. an onboard Application Process) and the user of the Service (i.e. a ground system). The MLDesigner PUS Model The MLDesigner PUS model is comprised of three major modules ground station (sending) satellite ground station (receiving) 1

2 The sending station sends configuration commands to the satellite. The satellite receives the commands, processes them, and, when necessary, sends messages to the receiving station. The top-level model PUS model shows the three major modules. generates & sends Telecommand-Packets displays received Telemetry-Packets Bodenstation Sender Satellite - Data Handling System Bodenstation Receiver Figure 1: PUS top-level model The sending ground station is essentially a large command system with a repertoire of control packets to send to the satellite. File ReadFileIVector#1 CreateTCPacket#1 Out_Packet 14.2 StringToIVector#1 DSToString# StringToIVector#3 TkText.input=1# StringToIVector# StringToIVector#4 The subsystem below keeps the simulation alive even when there are no events generated by the buttons StringToIVector#5 Clock#1 BlackHole# StringToIVector# StringToIVector# StringToIVector#8 3.1 StringToIVector#9 3.3 StringToIVector# StringToIVector# StringToIVector#12 Figure 2: Sending ground station 2

3 The module is linked to a Tcl control panel which is used to select the commands dynamically during simulation. When the appropriate button is pressed, the sending station module generates the appropriate control packet and sends it to the satellite model. A keep-alive circuit keeps the system operating where there are no commands. Figure 3: The PUS dynamic control panel 3

4 The satellite model consists of an uplink a router that sends received packets to applications services or downlink, a downlink, an applications module, a services module, and a housekeeping module. CRC or ISO Check send Packets to Application or Downlink In_Packet UpLink PacketRouter DownLink Out_Packet M Init All_TM_Servs V to Applications All_Applications HouseKeping, StorageControl, DataPool String2ServiceVector V to Services Providers write All_TM_Servs All_Services Error_Display The packet router is shown below. Figure 4: The satellite module Telecommand Packet => Packet-Type = 1 Telemetry Packet => Packet-Type = 0 In_Packet if PacketType == 1 then send to an application else send to downlink getpackettype Switch Packet (TC or TM) if TM-Packet Out_toDownLink if TC-Packet getapid Receive from Application 0 Call Application Application not Found Application found Goto Error Display Figure 5: Packet router 4

5 The applications module shows two applications. M All_TM_Servs User Application APID=3 StorageControl Application App = 1027 Figure 6: Applications module The services module lists all the services provided by this PUS model. M All_TM_Servs Telecommand-Services Telemetry-Services Telecommand Verification Services Transmission Control Service TestServices StorageControl Services Housekeeping Service Service 1.1 Service 14.1 Service 17.1 Service 15.1 Service 3.1 Service 1.2 Service 14.2 Service 17.2 Service 15.2 Service 3.3 Service 1.3 Service 15.3 Service 3.5 Service 1.4 Service 15.4 Service 3.6 Service 1.7 Service 15.5 Service 3.9 Service 1.8 Service 15.7 Figure 7: Services module 5

6 In_Packet PackettoString#1 Display#1 Figure 8: Receiving ground station Dynamic windows show the receipt of various types of packets. Three of these windows are shown below. Figure 9: Sent packet Figure 10: Storage application Note: Model developed by Peter Unger. Figure 11: Error window 6