Spacecraft Interface as described in THMSYS101 IDPUtoProbe ICD

Spacecraft Interface as described in THM-SYS-101 IDPU-to-Probe ICD Rev E Ellen Taylor University of California - Berkeley THEMIS IDPU PDR SC INTERFACE- 1 UCB, October 16, 2003

Power Service Characteristics Probe +28 V 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 100 ms 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-10 KHz effective line impedance in the service at the instrument connector THEMIS IDPU PDR SC INTERFACE- 2 UCB, October 16, 2003

Power Load Characteristics IDPU +28 V Load Characteristics • Service: Supplies core IDPU and instrument electronics • Grounding: 28 V service load shall return its current through the provided return line. The 28 V return shall be isolated from signal and chassis ground by at least 1 Mohm and no more than 1 F. • Inrush and Transients: <10 A for 1 msec; < Peak power consumption after 10 ms • Current Ripple: Current ripple defined in ICD figure • Power Consumption: Power consumption per THM-SYS-009 (by mode) Actuator +28 V Load Characteristics • Service: Supplies transient actuator loads for boom deployment (EFI Spin Plane Boom (SPB) Motors and Mag Boom Actuators) • Inrush and Transients: <10 A for 1 msec; < Peak power consumption after 10 ms • Current Ripple: TBD • Power Consumption: Power consumption per THM-SYS-009 THEMIS IDPU PDR SC INTERFACE- 3 UCB, October 16, 2003

Signal Interface Signal Characteristics • RS-422 Interface as shown in Figure 4 -2: RS-422 Interface THEMIS IDPU PDR SC INTERFACE- 4 UCB, October 16, 2003

Timing Interface • 8 MHz Clock: Square wave at 2^23 Hz (F 8 MHZ= 8, 388, 608 Hz), based on the stable spacecraft clock • 1 Hz Pulse: Pulse occurring once per second, based on the stable spacecraft clock as described in Figure 4 -3: Clock Signal Timing THEMIS IDPU PDR SC INTERFACE- 5 UCB, October 16, 2003

Command TLM Interface Command 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. 4 k 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: Low Speed Command Telemetry Interface THEMIS IDPU PDR SC INTERFACE- 6 UCB, October 16, 2003

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 THEMIS IDPU PDR SC INTERFACE- 7 UCB, October 16, 2003

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 YSI 44908 (311 P 18 -08 S 7 R 6). 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 THEMIS IDPU PDR SC INTERFACE- 8 UCB, October 16, 2003

Connectors & Harnessing • GSFC type S-311 -P-4 or equivalent • IDPU-J 101 9 -pin normal density male D connector on LVPS box • IDPU-J 201 9 -pin normal density female D connector on PCB front panel Table 4‑ 1: Connector IDPU-J 101 Pinout Pin Signal Table 4‑ 2: Connector IDPU-J 201 Pinout Harness Pin Signal Harness 1 IDPU Switched 28 V #22 TSPN w/ 6 1 Actuator 28 V #22 TSPN w/ 6 2 IDPU Switched 28 V #22 TSPN w/ 7 2 Actuator 28 V #22 TSPN w/ 7 3 IDPU Switched 28 V #22 TSPN w/ 8 3 Actuator 28 V #22 TSPN w/ 8 4 IDPU Thermistor #24 4 Unused 5 IDPU Thermistor Return #24 5 Unused 6 IDPU 28 V Return #22 TSPN w/ 1 6 Actuator 28 V Return #22 TSPN w/ 1 7 IDPU 28 V Return #22 TSPN w/ 2 7 Actuator 28 V Return #22 TSPN w/ 2 8 IDPU 28 V Return #22 TSPN w/ 3 8 Actuator 28 V Return #22 TSPN w/ 3 9 Unused 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). THEMIS IDPU PDR SC INTERFACE- 9 UCB, October 16, 2003

Connectors & Harnessing • GSFC type S-311 -P-4 or equivalent • IDPU-J 101 25 -pin normal density male D connector on DCB front panel Table 4‑ 3: Connector IDPU-J 301 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). THEMIS IDPU PDR SC INTERFACE- 10 UCB, October 16, 2003

Command Data Interchange Command Interface • Periodic synchronization command once per second containing a fixed size block of data • Transmission starts between 0 ms and 100 ms after the 1 Hz 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: Command Block Format THEMIS IDPU PDR SC INTERFACE- 11 UCB, October 16, 2003

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: Spacecraft Status Segment Format Time • Spacecraft clock time in UTC (4 bytes plus 2 bytes of sub seconds) at the time of the next 1 Hz 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 THEMIS IDPU PDR SC INTERFACE- 12 UCB, October 16, 2003

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 THEMIS IDPU PDR SC INTERFACE- 13 UCB, October 16, 2003

Telemetry Data Interchange Low Speed Telemetry Interface • Fixed-size “Housekeeping Telemetry Block” of data once per second • Transmission starts between 0 ms and 100 ms after the 1 Hz Clock pulse, and completes in no more than 500 ms • Includes an Instrument State of Health (SOH) packet and a Flux Gate Magnetometer (FGM) packet • Format is detailed in Table 4‑ 8: Housekeeping Telemetry Block Format THEMIS IDPU PDR SC INTERFACE- 14 UCB, October 16, 2003

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 THEMIS IDPU PDR SC INTERFACE- 15 UCB, October 16, 2003

Mechanical 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 THEMIS IDPU PDR SC INTERFACE- 16 UCB, October 16, 2003

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 THEMIS IDPU PDR SC INTERFACE- 17 UCB, October 16, 2003