A Deep Space Radio Communications Link for Cubesats: 3 The CU-E Communication Subsystem

John S. Sobtzak, Elie G.Tianang, Varun Joshi, Breana M. Branham, Neeti P. Sonth, Michael DeLuca, Travis Moyer, Kyle Wislinsky, and Dr. Scott E. Palo College of Engineering & Applied Science, University of Colorado at Boulder

The Challenge! The CU-E3 Solution Key Notes

3 CU's Earth Escape Explorer (CU-E ) Rx_C-Band_Patch 3 Gain dBi The University of Colorado's - Earth Escape Explorer (CU-E ) Rx_LNA Rx_PCB Rx_UHF is a 6U cubesat being designed and built to compete in Pasternack Astronautical NASA's Cube Quest Challenge - Deep Space Derby. PE15A1010 Rx_Mixer Development NF dB Lithium - 2 CU-E3 will be attempting communication from ≥ 4,000,000 Mini-Circuits Rx_IF_BPF Gain dB SIM-73L+ km, requiring us to “escape” the influence of the “Earth” and Lark Engineering

“explore” deep space. Rx_COAX_1 Rx_COAX_2 Rx_COAX_3 Rx_COAX_4 RF = 5210 MHz I IF = 450 MHz R L NASA’s Cube Quest Challenge LO = 4770 MHz o The Cube Quest Challenge has two phases: Rx_VCO_Amp † Analog Devics 1. Ground Tournaments (GT-1 thru GT-4) : C-BAND UPLINK HMC3587 XB1 CDH Rx_UHF - Maximum of $100,000 for any one team. RS422 - Phase completed in June 2017. 5182 MHz 2. The "In-space Prizes": Rx_OCXO Taitien - 365-day competition period. XO-0087_TT a) Lunar Derby Rx_PLL_VCO LF 100 MHz Reflectarray & Horn Antennas Analog Devices • Up to $3 million in prizes. 3 HMC833LP6GE PLL o CU-E utilizes a novel, student-designed, reflectarray • Technical objectives in propulsion & – MHz XB1 CDH Rx_PLL_VCO XB1 antenna and feed horn. communications. SPI CDH/FSW • Planar design → fits 6U cubesat form factor. b) Deep Space Derby • Utilizes standard PCB microstrip technology. • Up to $1.5 million in prizes. ADCS → easy and relatively inexpensive to fabricate. • Focus on deep space communications Tx_Reflect_Array • High gain → 22.3 dB at X-band Tx frequency. using small spacecraft. Gain = 22.3 dBi Tx_Hybrid_1 • Competition starts at 4,000,000 km: Anaren EPS X-BAND DOWNLINK o 3 Tx_COAX_5 1E0018-3 CU-E ’s design includes a second feed horn antenna. i. Best Burst Data Rate - $250,000 RL dB IL dB ii. Largest Aggregate Data - $750,000 EIRP IL dB 8447.6 MHz • Provides back-up communication link in the event iii. Spacecraft Longevity - $250,000 +56.6 dBm Tx_COAX_3 primary reflectarray antenna does not deploy. XB1 CDH Tx_HRCCS_FPGA iv. Farthest Communication - $250,000 +34.5 dBm IL dB • Lower gain → 12.8 dB, but can still close link. Tx_PA_PCB RS422 3 nd Tx_SW † CU-E placed 2 during the Ground Tournament phase, Tx_COAX_6 Tx_PA Dow-Key Microwave Tx_PA_VR IL dB Analog Devices High-Rate CubeSat Communication System earning $80,000, and has been offered a position on the 401T-420832 Linear Technologies HMC7357LP5GE ‡ SLS’s EM-1 mission!!! RL dB LT8610AC Tx_HRCCS_PCB (HRCCS) P1dB dBm IL dB η A HRCCS 3 PAE o CU-E will provide the maiden launch for the HRCCS. CU/NASA/LASP 3 Challenges Faced by CU-E Tx_COAX_2 Bias 8.9 V Voltage • Designed for deep space X-band frequencies. IL dB Controller Regulator • Provides a flexible communications platform. o Size – restricted to 6U dimensions. +35.1 dBm Processor/ FPGA • Limits power generation and heat dissipation. 8.0 V Vgg • Compatible with NASA’s NEN & DSN.

• Limits transmitter power. Tx_Feed_Horn LO • Limits use of classic high-gain antennas. Tx_COAX_1 Gain = 12.8 dBi Tx_Hybrid_2 I Downlink Budget Analysis Summary → Limits possible radiated signal strength (EIRP)! R L TX ANTENNA Reflect Feed Reflect Feed Reflect Feed Anaren - o 1E0018-3 Array Horn Array Horn Array Horn Limited time & money! Tx_COAX_7 +35.5 dBm RF = 8447.6 MHz SLANT RANGE km 4,000,000 6,000,000 27,000,000 RL dB Quad • GTs’ schedule very short & tight. IL dB TRANSMITTED EIRP dBm 56.6 47.1 56.6 47.1 56.6 47.1 EIRP IL dB Modulator • Rad-hardened parts too expensive. TOTAL SIGNAL POWER @ OUTPUT OF LNB (S) dBm -82.4 -91.9 -85.9 -95.4 -99.0 -108.5 +47.1 dBm NOISE POWER DENSITY OF RX @ OUTPUT OF LNB (No) dBm/Hz -123.0 -123.0 -123.0 -123.0 -123.0 -123.0 → Could not design everything from scratch. +34.5 dBm Tx_COAX_4 NOISE POWER OF RX (N) dBm -94.3 -103.8 -97.9 -107.4 -111.0 -112.2 → Use COTS components as much as possible. IL dB USEFUL BIT RATE bits/s 608 68 270 30 13 1 → Prototype circuits quickly for P.O.C & testing. ENERGY PER BIT (Eb) W/bit -110.3 -110.2 -110.3 -110.2 -110.1 -108.5 Tx_COAX_8 Received SNR (@ OUTPUT OF LNB) dB 11.9 11.9 11.9 12.0 12.0 3.7 o Distance – extremely long range. IL dB Resulting Eb/No dB 12.7 12.7 12.7 12.8 12.8 14.5 Link Margin dB 6.10 6.12 6.11 6.15 6.22 7.86 → EVERY dB COUNTS!!!

‡Palo, S.E., “High Rate Communications for CubeSats”, Proc. of the IEEE International Microwave Symposium, Phoenix, AZ, 2015. SSC17-P1-07 ‡ Palo, S.E., D. O’Connor, E. DeVito, R. Kohnert, G. Crum and S. Altunc, “Expanding CubeSat Capabilities with a Low Cost Transceiver”, Proc. of the AIAA Small Satellite Conference, Logan, UT, 2014.