Implementation of Iridium Transmitter

1805-EX-ST-2017 Text Documents

Rocket Lab USA

2017-12-19ELS_202553

ROCKET LAB PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Rocket Lab Orbital Launch Vehicle Iridium 9602 SBD (FCC ID: Q639602) Implementation Version 1.0 22 November 2017 N. Altman Rev 1.0 ROCKET LAB 1 PROPRIETARY

Contents 1 MISSION OVERVIEW .................................................................................................................. 3 2 IMPLEMENTATION ..................................................................................................................... 4 2.1 System Block Diagram ........................................................................................................... 4 2.2 System Description ................................................................................................................. 4 2.3 Antenna Hardware .................................................................................................................. 4 2.4 Antenna Locations .................................................................................................................. 5 3 ANTENNA PATTERNS ................................................................................................................ 6 4 OVER-THE-AIR TESTING ........................................................................................................... 7 5 CONTROL OF TRANSMISSION DIRECTION ........................................................................... 8 6 EMERGENCY SHUT-OFF ............................................................................................................ 8 Rev 1.0 ROCKET LAB 2 PROPRIETARY

1 MISSION OVERVIEW The Electron launch vehicle is a 3-stage commercial launch vehicle manufactured and operated by Rocket Lab, launched from Rocket Lab’s private orbital launch range in Mahia, New Zealand. The Electron launch vehicle is licensed by the Federal Aviation Authority (FAA). The launch vehicle lifts off shortly after ignition of all Stage 1 motors. At T+150 seconds, the propellant in Stage 1 is exhausted and the motors cut off. Stage1/2 Separation occurs at T+153 seconds and the single Stage 2 motor ignites at T+157 seconds. The vehicle achieves orbit at T+491 seconds (perigee altitude reaches 130 km). The Stage 2 motor cuts off at T+493 seconds, and Stage2/3 separation occurs shortly afterward. Following separation from the rocket booster stage, Stage 3 completes a 45-minute coast, followed by an ignition, cutting off at T+3028 seconds. Payload separation occurs at T+3059 seconds. Rocket Lab has implemented an experimental communications module using the Iridium 9602 transceiver for the upcoming experimental test launch. The Iridium 9602 transmitter is activated once the vehicle is in orbit, following Stage2/3 separation. The Iridium 9602 module continues transmit beacon data for the duration of the Stage 3 coast, burn, and payload separation, until the Stage 3 batteries deplete or the transmitter is commanded off. There is no mechanism to charge the batteries on the spacecraft, therefore the duration of the Iridium 9602 transmission is limited by the life of the batteries, maximum 11 hours. Iridium 9602 Transmitter Active Figure 1 - Electron Launch Vehicle Mission Overview Rev 1.0 ROCKET LAB 3 PROPRIETARY

2 IMPLEMENTATION 2.1 System Block Diagram Figure 2 - Iridium 9602 System Block Diagram 2.2 System Description The Iridium transmitter used on the vehicle upper stage is the Iridium 9602 (FCC ID: Q639602). The transmitter is used default configuration settings consistent with its existing FCC license for ground- to-space communications. The transmitter is connected to the Stage 3 Flight Computer, which sends SBD messages to the module via serial communication. The Flight Computer interrogates the 9602 module for health and status and signal strength information. The antennas used for the Iridium 9602 transceiver are L-Band rounded blade antennas. Polarization: Linear, predominantly vertical. An electromechanical RF relay is used to select the transmission path from the Iridium 9602 to either antenna. 2.3 Antenna Hardware Figure 3 - Iridium 9602 Antenna Rev 1.0 ROCKET LAB 4 PROPRIETARY

2.4 Antenna Locations Two L-Band rounded blade antennas are located 180° apart on Stage 3. An electromechanical switch is used to control the direction of transmission. Antenna 2 170° Antenna 2 Antenna 1 Antenna 1 350° Figure 4 - Iridium 9602 Antenna Locations Rev 1.0 ROCKET LAB 5 PROPRIETARY

3 ANTENNA PATTERNS Test Frequency: 1616.25 MHz Polarization: Vertical and Horizontal Rev 1.0 ROCKET LAB 6 PROPRIETARY

4 OVER-THE-AIR TESTING System-level tests were conducted during integrated stage testing on the combined Stage 2 / Stage 3 and Stage 3 live-sky test. Beacon messages were transmitted to the Iridium 9602 SBD transceiver with the stage placed outside with a view of the sky. Messages were received via the Rock-Block web-based portal. All messages were received. Rev 1.0 ROCKET LAB 7 PROPRIETARY

5 CONTROL OF TRANSMISSION DIRECTION In order to prevent interference with Radio Astronomy, the Rocket Lab communications system ensures that transmissions will only occur on an Iridium 9602 antenna that is pointed away from the earth. This is implemented using the launch vehicle’s navigation system and control of an electromechanical RF switch to select the desired antenna for transmission. The Electron launch vehicle is equipped with a 6-degree-of-freedom navigation system based on an inertial measurement unit (IMU) and GPS. The navigation algorithm used to control the launch vehicle computes altitude, position, and velocity relative to the earth. The Electron flight computer has data for the location of each antenna relative to the vehicle body axis. Using a combination of vehicle altitude, vehicle position, and antenna pointing direction, the angle between the nadir and axis of transmission of each antenna is computed. The direction of transmission is selected such that (a) the transmission is directed towards the Iridium constellation, and (b) radio-frequency transmission is not directed towards earth. Since the Iridium constellation (780km) is higher altitude than the Electron orbit (500km), both conditions are met. 6 EMERGENCY SHUT-OFF The Rocket Lab communications module shuts down transmissions from the Iridium 9602 if any errors are detected. Rocket Lab can shut down operation of one or all launch vehicle transmitters by sending commands through the vehicle’s UHF telemetry link. Rev 1.0 ROCKET LAB 8 PROPRIETARY


Document Created: 2017-11-25 19:24:50
Document Modified: 2017-11-25 19:24:50
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