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

A Deep Space Radio Communications Link for Cubesats: The CU-E3 Communication Subsystem

The CU-E3 Solution CU's Earth Escape Explorer (CU-E3)

The University of Colorado's - Earth Escape Explorer (CU-E3) is a 6U cubesat being designed and built to compete in NASA's Cube Quest Challenge - Deep Space Derby. CU-E3 will be attempting communication from ≥ 4,000,000 km, requiring us to “escape” the influence of the “Earth” and “explore” deep space.

NASA’s Cube Quest Challenge

o The Cube Quest Challenge has two phases:

1. Ground Tournaments (GT-1 thru GT-4)†: - Maximum of $100,000 for any one team. - Phase completed in June 2017.

2. The "In-space Prizes": - 365-day competition period.

a) Lunar Derby • Up to $3 million in prizes. • Technical objectives in propulsion &

communications.

b) Deep Space Derby • Up to $1.5 million in prizes. • Focus on deep space communications

using small spacecraft. • Competition starts at 4,000,000 km:

i. Best Burst Data Rate - $250,000 ii. Largest Aggregate Data - $750,000 iii. Spacecraft Longevity - $250,000 iv. Farthest Communication - $250,000

† CU-E3 placed 2nd during the Ground Tournament phase, earning $80,000, and has been offered a position on the SLS’s EM-1 mission!!!

Challenges Faced by CU-E3

o Size – restricted to 6U dimensions. • Limits power generation and heat dissipation. • Limits transmitter power. • Limits use of classic high-gain antennas.

→ Limits possible radiated signal strength (EIRP)!

o Limited time & money! • GTs’ schedule very short & tight. • Rad-hardened parts too expensive.

→ Could not design everything from scratch. → Use COTS components as much as possible. → Prototype circuits quickly for P.O.C & testing.

o Distance – extremely long range. → EVERY dB COUNTS!!!

The Challenge!

Reflectarray & Horn Antennas

o CU-E3 utilizes a novel, student-designed, reflectarray antenna and feed horn.

• Planar design → fits 6U cubesat form factor. • Utilizes standard PCB microstrip technology.

→ easy and relatively inexpensive to fabricate. • High gain → 22.3 dB at X-band Tx frequency.

o CU-E3’s design includes a second feed horn antenna.

• Provides back-up communication link in the event primary reflectarray antenna does not deploy.

• Lower gain → 12.8 dB, but can still close link.

High-Rate CubeSat Communication System (HRCCS)‡

o CU-E3 will provide the maiden launch for the HRCCS.

• Designed for deep space X-band frequencies. • Provides a flexible communications platform. • Compatible with NASA’s NEN & DSN.

Downlink Budget Analysis Summary

Key Notes

SSC17-P1-07

TX ANTENNA-

Reflect

Array

Feed

Horn

Reflect

Array

Feed

Horn

Reflect

Array

Feed

Horn

SLANT RANGE km

TRANSMITTED EIRP dBm 56.6 47.1 56.6 47.1 56.6 47.1

TOTAL SIGNAL POWER @ OUTPUT OF LNB (S) dBm -82.4 -91.9 -85.9 -95.4 -99.0 -108.5

NOISE POWER DENSITY OF RX @ OUTPUT OF LNB (No) dBm/Hz -123.0 -123.0 -123.0 -123.0 -123.0 -123.0

NOISE POWER OF RX (N) dBm -94.3 -103.8 -97.9 -107.4 -111.0 -112.2

USEFUL BIT RATE bits/s 608 68 270 30 13 1

ENERGY PER BIT (Eb) W/bit -110.3 -110.2 -110.3 -110.2 -110.1 -108.5

Received SNR (@ OUTPUT OF LNB) dB 11.9 11.9 11.9 12.0 12.0 3.7

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

4,000,000 6,000,000 27,000,000

‡Palo, S.E., “High Rate Communications for CubeSats”, Proc. of the IEEE International Microwave Symposium, Phoenix, AZ, 2015.

‡ 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.

XB1

I

LR

LO

XB1 CDH Tx_HRCCS_FPGA

RS422

EIRP

+56.6 dBm

C-BAND UPLINK

5182 MHz

Rx_IF_BPFLark Engineering

LO = 4770 MHz

+35.5 dBm

PLL

Rx_OCXOTaitien

XO-0087_TT

100 MHz

Rx_PCB

CDH/FSW

ADCS

EPS

Rx_COAX_2IF = 450 MHz

LF

X-BAND DOWNLINK

8447.6 MHz

Tx_PA_PCB

RF = 5210 MHzRx_COAX_1

Rx_MixerMini-Circuits

SIM-73L+

Rx_LNAPasternack

PE15A1010

NF dB

Gain dB

Rx_C-Band_PatchGain dBi

Rx_PLL_VCOAnalog Devices

HMC833LP6GE

– MHz

Rx_VCO_AmpAnalog Devics

HMC3587

Rx_COAX_3 Rx_COAX_4

Tx_PAAnalog Devices

HMC7357LP5GE

P1dB dBm

PAE

Tx_SWDow-Key Microwave

401T-420832

RL dB

IL dB

Tx_PA_VRLinear Technologies

LT8610AC

η A

Tx_COAX_2IL dB

8.0 V

8.9 V

Vgg

Bias

Controller

Tx_HRCCS_PCB

Voltage

Regulator

Processor/

FPGA

RF = 8447.6 MHz

L

R

I

Rx_UHFAstronautical

Development

Lithium - 2

Quad

Modulator

Tx_COAX_1

HRCCS

CU/NASA/LASP

Tx_Hybrid_1Anaren

1E0018-3

RL dB

IL dB

+35.1 dBm

Tx_COAX_3IL dB

Tx_COAX_4IL dB

Tx_Hybrid_2Anaren

1E0018-3

RL dB

IL dB

Tx_Feed_HornGain = 12.8 dBi

Tx_Reflect_ArrayGain = 22.3 dBi

Tx_COAX_5IL dB

Tx_COAX_6IL dB

Tx_COAX_7IL dB

Tx_COAX_8IL dB

+34.5 dBm

+34.5 dBm

EIRP

+47.1 dBm

XB1 CDH Rx_PLL_VCO

SPI

XB1 CDH Rx_UHF

RS422