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Spacecraft Interface as described in THM-SYS-101 IDPU-to-Probe ICD Rev E Ellen Taylor

Spacecraft Interface as described in THM-SYS-101 IDPU-to-Probe ICD Rev E Ellen Taylor University of California - Berkeley. Power Service Characteristics. Probe +28V Service Characteristics Services : Two separately switched services (IDPU and Actuator Interface) Regulation : 28 +/-6 V

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Spacecraft Interface as described in THM-SYS-101 IDPU-to-Probe ICD Rev E Ellen Taylor

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  1. Spacecraft Interface • as described in THM-SYS-101 IDPU-to-Probe ICD Rev E • Ellen Taylor • University of California - Berkeley

  2. Power Service Characteristics • Probe +28V Service Characteristics • Services: Two separately switched services (IDPU and Actuator Interface) • Regulation: 28 +/-6 V • Ripple: function of frequency, defined in ICD figure • Transients: less than +/- 2 Volts for 1 msec on supply lines • Current Limits: Act like circuit breakers, require ground-commanded reset and including an override capability, shall not trip on transients less than 100ms in duration, negative currents, or by the in-rush current specified • Current Monitors: On each instrument power service and included in the spacecraft State of Health telemetry • Returns: Separate return line for each service • Harness: Service and return lines twisted pairs of #22 AWG wire, shielded, connected to spacecraft chassis ground at the signal source end • Impedance: < 500 milliohms DC-10KHz effective line impedance in the service at the instrument connector

  3. Power Load Characteristics • IDPU +28V Load Characteristics • Service: Supplies core IDPU and instrument electronics • Grounding: 28V service load shall return its current through the provided return line. The 28V return shall be isolated from signal and chassis ground by at least 1 Mohm and no more than 1F. • Inrush and Transients: <10A for 1 msec; < Peak power consumption after 10ms • Current Ripple: Current ripple defined in ICD figure • Power Consumption: Power consumption per THM-SYS-009 (by mode) • Actuator +28V Load Characteristics • Service: Supplies transient actuator loads for boom deployment (EFI Spin Plane Boom (SPB) Motors and Mag Boom Actuators) • Inrush and Transients: <10A for 1 msec; < Peak power consumption after 10ms • Current Ripple: TBD • Power Consumption: Power consumption per THM-SYS-009

  4. Signal Interface • Signal Characteristics • RS-422 Interface as shown in Figure 4-2 • Figure 4-2: RS-422 Interface

  5. Timing Interface • Timing Interface • 8MHz Clock: Square wave at 2^23Hz (F8MHZ= 8,388,608 Hz), based on the stable spacecraft clock • 1Hz Pulse: Pulse occurring once per second, based on the stable spacecraft clock as described in Figure 4-3. • Figure 4-3: Clock Signal Timing

  6. Command and TLM Interface • Command and Low Speed Telemetry Interface • Serial command interface used to send data from the spacecraft to the IDPU • Serial telemetry interface used to send status, housekeeping and FGM data from the IDPU to the spacecraft • Transmitted on single serial lines (one for command, one for telemetry) using UART encoding, and differential interface • Data transmitted at 38.4k baud, with 1 start bit (asserted low), 8 data bits, 1 parity bit (even), and one stop bit (active high) per 8-bit byte transmitted, as shown in Figure 4‑4 • Figure 4‑4: Low Speed Command and Telemetry Interface

  7. High Speed TLM Interface • High Speed Telemetry Interface • Bit serial interface used to send full CCSDS telemetry frames from the IDPU to the spacecraft Bus Avionics Unit (BAU). Characteristics and Timing in Figure 4-5. • Figure 4‑5: High Speed Telemetry Interface

  8. Thermistor and Sun Interface • Thermistor Interfaces • One passive thermistor interface will be conditioned, converted, and telemetered by probe • IDPU monitors the temperatures of the rest of the instrument systems when it is powered on • Yellow Springs YSI44908 (311P18-08S7R6). • Sun Pulse Interface • Provided to the IDPU once per spin, indicating the sun crossing. • Single ended • More definition required • Figure 4‑6: Sun Pulse Interface

  9. Pin Signal Harness Pin 1 Signal Actuator 28V #22 TSPN w/ 6 Harness 2 1 IDPU Switched 28V Actuator 28V #22 TSPN w/ 6 #22 TSPN w/ 7 2 3 IDPU Switched 28V Actuator 28V #22 TSPN w/ 7 #22 TSPN w/ 8 3 4 Unused IDPU Switched 28V #22 TSPN w/ 8 4 5 Unused IDPU Thermistor #24 6 5 Actuator 28V Return IDPU Thermistor Return #22 TSPN w/ 1 #24 7 6 IDPU 28V Return Actuator 28V Return #22 TSPN w/ 2 #22 TSPN w/ 1 8 7 IDPU 28V Return Actuator 28V Return #22 TSPN w/ 2 #22 TSPN w/ 3 9 8 IDPU 28V Return Unused #22 TSPN w/ 3 9 Unused Connectors • Connectors & Harnessing • GSFC type S-311-P-4 or equivalent • IDPU-J101 9-pin normal density male D connector on LVPS box • IDPU-J201 9-pin normal density female D connector on PCB front panel Table 4‑1: Connector IDPU-J101 Pinout Table 4‑2: Connector IDPU-J201 Pinout TSPN is a twisted-shielded pair with shield not connected (at this end). TSPS is a twisted shielded pair with shield terminated on the connector backshell (if backshell is used).

  10. Connectors • Connectors & Harnessing • GSFC type S-311-P-4 or equivalent • IDPU-J101 25-pin normal density male D connector on DCB front panel Table 4‑3: Connector IDPU-J301 Pinout TSPN is a twisted-shielded pair with shield not connected (at this end). TSPS is a twisted shielded pair with shield terminated on the connector backshell (if backshell is used).

  11. Command Data Interchange • Command Interface • Periodic synchronization command once per second containing a fixed size block of data • Transmission starts between 0ms and 100ms after the 1Hz Clock pulse, and completes in no more than 500 ms • Includes a spacecraft status segment and a command segment • The command block format is detailed in Table 4‑4 • Table 4‑4: Command Block Format

  12. Spacecraft Status Segment • Spacecraft Status Segment • Includes information on the status of the spacecraft bus, generated automatically on board by the spacecraft processor • Format shown in Table 4‑5 • Table 4‑5: Spacecraft Status Segment Format • Time • Spacecraft clock time in UTC (4 bytes plus 2 bytes of sub seconds) at the time of the next 1Hz clock tick • Ordered MSB first • Status Field • Consists of 8 bytes of data indicating Spacecraft status to the IDPU • Complete definition of the Status field is still TBD

  13. Command Segment • Command Segment • Contains instrument real-time command packets received by the probe in the previous second and time-tagged commands that were scheduled for execution in the previous second • The probe shall copy all instrument command packets into buffer sequentially, with the unused portion at the end being filled with the TBD fill data pattern • Instrument commands are identified by having APIDs over 400 Hex. • Commands limited to 1000 bytes in length • If buffer gets full, unsent commands are lost and an error is reported in the probe telemetry • Only full commands shall be included in the Command Segment, no partial commands • The probe forwards command packets to the IDPU with the format described in the ICD

  14. Telemetry Data Interchange • Low Speed Telemetry Interface • Fixed-size “Housekeeping Telemetry Block” of data once per second • Transmission starts between 0ms and 100ms after the 1Hz Clock pulse, and completes in no more than 500ms • Includes an Instrument State of Health (SOH) packet and a Flux Gate Magnetometer (FGM) packet • Format is detailed in Table 4‑8 • Table 4‑8: Housekeeping Telemetry Block Format

  15. Telemetry Data Interchange • State Of Health Packet • Includes essential engineering data which the probe stores and includes in its telemetry stream • Format of the SOH packet is described in ICD • Format • Flux Gate Magnetometer Packet • Includes engineering data from the Instrument’s Flux Gate Magnetometer used for Probe Attitude Determination • Format of the FGM packet is described in ICD • Length • High Speed Telemetry Interface • The high-speed telemetry interface shall be used to transfer CCSDS-formatted instrument telemetry frames as described in THM-SYS-115 THEMIS Telemetry Format Specification

  16. Mechanical Interface • Interface Drawing • Mechanical configuration provided in the IDPU ICD Drawing shown in IDPU Mechanical Presentation • Details envelope, mounting, and connector locations, CG location, and coordinates • Mass Properties • Instrument Mass Spreadsheet shows the instrument mass properties, including current best estimate and maximum (with reserve) • FOV and Alignment • The IDPU VME chassis requires no FOV or special alignment

  17. Thermal Interface • Thermal Design • Addresses radiative and conductive heat transfer between the IDPU and Probe • Thermal Design Responsibilities • UCB delivers the IDPU thermal model to Swales for inclusion in the top-level spacecraft thermal model. Swales verifies thermal design meets the instrument thermal constraints for all expected spacecraft configurations • Thermal Information provided in ICD (shown previously) • Surface Properties and Thermal Conduction • IDPU Power Dissipation • Heater Requirements (none) • Temperature Requirements

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