Communications Policy

Overall: PASS

This is a screening-level RF subsystem and link-budget closure for the released 600 km SSO concept. It is not a substitute for licensed-frequency coordination, measured antenna patterns, or a ground-network service agreement.

Checks

• PASS communications_configuration_block_present
• PASS communications_descriptor_fields_complete
• PASS communications_hardware_complement_complete
• PASS communications_power_budget_consistent
• PASS physical_communications_geometry_complete
• PASS communications_link_definitions_complete
• PASS communications_command_uplink_margin_closes
• PASS communications_science_downlink_margin_closes
• PASS communications_telemetry_downlink_margin_closes
• PASS communications_link_budget_uses_released_hardware
• PASS communications_science_volume_definition_complete
• PASS communications_daily_science_return_closes
• PASS communications_cdh_interface_rate_closes

RF architecture

• Architecture: cold-redundant X-band science downlink with dual electronically steered arrays and S-band command/telemetry coverage
• Active communications load: 112.000 W of 120.000 W.
• Installed RF hardware mass: 36.600 kg.

Link budgets

• science_downlink: x_band at 8.200 GHz, 250.000 Mbps, maximum slant range 2000.0 km, Eb/N0 24.386 dB, margin 19.886 dB (minimum 3.000 dB).
• telemetry_downlink: s_band at 2.250 GHz, 1.000 Mbps, maximum slant range 2000.0 km, Eb/N0 24.078 dB, margin 19.078 dB (minimum 3.000 dB).
• command_uplink: s_band at 2.050 GHz, 0.064 Mbps, maximum slant range 2000.0 km, Eb/N0 42.845 dB, margin 37.845 dB (minimum 3.000 dB).

Science data return

• Released C&DH science generation: 19.241 Gbit/orbit, 288.622 Gbit/day.
• Representative access basis: 4 contacts/day at 600.0 s usable duration, 0.850 availability and 0.800 protocol efficiency.
• Effective science return: 408.000 Gbit/day; margin factor 1.414 (minimum 1.200).
• Ground-network screening assumption: Representative two-site 5 m class ground network; access counts remain a screening assumption pending the mission-operations and ground-segment concept.

Physical hardware

• x_band_transponder_pair (science_downlink_transponder): 2 x radiation_tolerant_x_band_qpsk_transmitter, mounted at avionics_tray_lower; parts comms_xband_transponder_1, comms_xband_transponder_2. Paired X-band transmitter enclosures conductively mounted at opposite outboard corners of the lower avionics tray and cross-strapped to both phased-array panels.
• s_band_transceiver_pair (command_telemetry_transponder): 2 x radiation_tolerant_s_band_transceiver, mounted at avionics_tray_upper; parts comms_sband_transceiver_1, comms_sband_transceiver_2. Paired S-band command/telemetry transceivers on the upper avionics tray with independent PCDU feeds and cross-strapped antenna-switch ports.
• rf_distribution_pair (rf_distribution_unit): 2 x dual_band_coaxial_switch_and_diplexer_unit, mounted at avionics_tray_lower; parts comms_rf_switch_1, comms_rf_switch_2. Redundant RF switch/diplexer enclosures on the lower tray route each transponder lane to either matching antenna chain without an unmodeled shared switch.
• x_band_phased_array_pair (science_antenna): 2 x electronically_steered_x_band_patch_array, mounted at bus_plus_x_and_minus_x_panels; parts comms_xband_array_1, comms_xband_array_2. Opposing electronically steered X-band arrays are fixed to the plus-X and minus-X bus side panels so either panel can return science data without a deployment mechanism.
• s_band_low_gain_antenna_set (command_telemetry_antenna): 4 x quadrature_s_band_patch_antenna, mounted at bus_plus_y_and_minus_y_panels; parts comms_sband_patch_1, comms_sband_patch_2, comms_sband_patch_3, comms_sband_patch_4. Two passive S-band patch antennas on each Y-side bus panel provide overlapping command and low-rate telemetry coverage around the spacecraft body.