Article Figures & Data
Figures
- FIGURE 1
SNUGLITE-III CubeSats: (a) joint 6U configuration; (b) separated SNUGLITE-III A/B CubeSats, each in an identical 3U configuration
- FIGURE 2
Operational scenario of the SNUGLITE-III CubeSats with precise relative navigation in formation flying, rendezvous, and docking phases
- FIGURE 3
Seoul National University CubeSat L1/L2C GPS receiver consisting of three GPS receivers on one board, before and after can shielding
- FIGURE 4
Overall block diagram of the relative navigation system
- FIGURE 5
LEO GPS simulation results for 6 h: (a) skyplot in the body frame when a GPS antenna is used in the +Y direction; (b) visible GPS PRNs
- FIGURE 6
Relative position error during LEO simulations in LVLH coordinates (a) for each axis and (b) with 3D normalization and DOP
- FIGURE 7
Results of enlarging the relative position error during LEO simulations in LVLH coordinates (a) for each axis and (b) with 3D normalization and the number of visible satellites (the red line represents the reference PRN)
- FIGURE 8
DTDDCP measurements distributed within the threshold set by a half-cycle slip
- FIGURE 9
Design of the PCB-based ground plane of the GPS patch antenna: engineering model (above) and flight model (below)
- FIGURE 10
Anechoic chamber setup for measuring the antenna pattern with a PCB-based ground plane: (a) antenna mounted in a chamber; (b) axis definition for the antenna pattern, where the Z-direction represents the main lobe
- FIGURE 11
Comparison of 3D antenna patterns with and without the ground plane for the main and back lobes (RHCP)
- FIGURE 12
Comparison of 3D antenna patterns with and without the ground plane for the main and back lobes (LHCP)
- FIGURE 13
Equipment settings for data collection
The same GPS signal can be received by connecting the high-cost receiver to the GPS patch antenna and the CubeSat receiver with a splitter.
- FIGURE 14
Experimental setup at the time of data collection: (a) GPS receivers and monitor PC; (b) GPS patch antennas and reference station settings; (c) skyplot in the body frame for 2 h in the ground environment
- FIGURE 15
Performance evaluation results of GPS measurements with a GPS patch antenna (yellow presents results for a high-cost GPS receiver and antenna as a reference): (a) carrier-to-noise ratio (C/N0) for satellite elevation in the presence or absence of a PCB-based ground plane; (b) DDPR residual error; (c) DDCP residual error
- FIGURE 16
DGPS relative position error during the experiment in LVLH coordinates (a) for each axis and (b) with 3D normalization and DOP
- FIGURE 17
RTK relative position error during the experiment in LVLH coordinates (a) for each axis and (b) with 3D normalization and the number of visible satellites (red and blue lines present the number of satellites; yellow and green lines present the reference PRN)
- FIGURE 18
DTDDCP measurements for cycle-slip detection for (a) the CubeSat GPS receiver and (b) the high-cost GPS receiver
Tables
- TABLE 1
System Configuration of the SNUGLITE-III CubeSats
DQPSK: differential quadrature phase-shift keying; GMSK: Gaussian minimum shift keying; UHF: ultra-high frequency
System Description Mass A 3.1 kg B 3.1 kg Dimensions Joint 100 x 226.3 x 340.5 mm (6U) Separated 100 x 100 x 340.5 mm (3U) Orbit 600 km, Sun-synchronous orbit Power Generation Undeployed 4.2 W Deployed 7.9 W Uplink UHF, AX.25, GMSK 9.6 kbps (telecommand) Downlink UHF, AX.25, GMSK 9.6 kbps (telemetry) S-Band, DQPSK, 1 Mbps (mission data) Inter-Satellite Link LoRa, Code rate: 4/8, Spreading factor: 6 (23.4 kbps), Bandwidth: 500 kHz, Maximum range: 55 km, Power consumption (in transit mode): 0.39 W Actuators Reaction wheel x3, Magnetorquer x3 - TABLE 2
Hardware Configuration for the Relative Navigation System
SNU: Seoul National University
Hardware Description OBC processor Atmel AT32UC3C 66 MHz, 91 DMIPS
(Gomspace Nanomind A3200)GPS receiver SNU dual-frequency (L1/L2C) space GPS receiver x3
(in-house)GPS antenna Tallysman TW3967 x3 ISL module LoRa SX1262MB2CAS x2 Parameter Specification Voltage 3.3 V Power 0.45 W Temperature –40 °C to +85 °C Mass 165 g (3 EA) Size PC/104 1/3 Standard (1 EA) 92 x 88.9 x 60.0 mm Interface UART, PPS Tracking channels (L1+L2C) 32 (maximum) Hardware for space Conformal coating (parylene C) Shield CAN NSPx (C7521) - TABLE 4
ISL Transmission Data For m GPS Visible Satellites
ECEF: Earth-centered, Earth-fixed
Variable Type Size [byte] GPS week uint16_t 2 GPS time of week uint32_t 4 User position in ECEF double*3 24 User velocity in ECEF double*3 24 Number of visible GPS satellites uint8_t 1 GPS PRN uint8_t*m 1*m Pseudorange double*m 8*m Carrier phase double*m 8*m Doppler float*m 4*m Carrier-to-noise power density uint8_t*m 1*m Total size 55+22*m Polarization Main Lobe [dBic] Back Lobe [dBic] without
ground planewith
ground planewithout
ground planewith
ground planeRHCP 18.07 19.19 10.95 10.77 LHCP 5.85 9.25 10.97 6.74 - TABLE 6
Experimental Environment Setup Conditions
SNU: Seoul National University; UTC: coordinated universal time
Parameter Details Date and time Sep-04-2023 13:30:00–15:30:00 (UTC+9) Location 37°14’34.707”N, 126°39’39.024’’E Elevation mask 10° (radial) Reference Trimble Business Center (post-processing) GPS receivers Reference Trimble R10 Target Trimble NetR9 (high-cost) SNU GPS receiver (CubeSat) Chaser Trimble NetR9 (high-cost) SNU GPS receiver (CubeSat) GPS antennas Tallysman TW3967 x2 GPS Receiver X [m] Y [m] Z [m] 3D [m] CubeSat 1.58 0.53 0.69 1.80 High-cost 1.01 0.27 0.36 1.10 GPS Receiver X [cm] Y [cm] Z [cm] 3D [cm] CubeSat 1.25 0.64 0.66 1.55 High-cost 1.26 0.55 0.57 1.49 GPS Receiver Success-fix rate [%] TTFF (mean) [s] CubeSat 100% 20.20 High-cost 100% 1.89
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