ADC	Analog-to-Digital Converter
BPSK	Binary Phase Shifting Keying
$B_w$	−3 dB Bandwidth
cGNSS-R	conventional Global Navigation Satellite Systems—Reflectometry
COTS	Commercial Off-The-Shelf
DAC	Digital-to-Analog Converter
DCM	Direction Cosine Matrix
DUT	Device Under Test
ECEF	Earth Centered Earth Fixed
$f_c$	Cut-off frequency at −3 dB
$f_{LO}$	LO frequency
FM	Frequency Modulation
G	Gain
GEROSS-ISS	GNSS rEflectometry, Radio Occultation and Scatterometry onboard the International Space Station
GLONASS	GLObalnaya NAvigatsionnaya Sputnikovaya Sistema
GNSS	Global Navigation Satellite Systems
GNSS-R	Global Navigation Satellite Systems—Reflectometry
GPS	Global Positioning System
GPS-DO	GPS Disciplined Oscillator
GSM	Global System for Mobile communications
G-TERN	GNSS Transpolar Earth Reflectometry exploriNg system
I	In-phase component
IF	Intermediate Frequency
iGNSS-R	interferometric Global Navigation Satellite Systems—Reflectometry
IMU	Inertial Measurement Unit
L	Losses, attenuation
LHCP	Left Hand Circular Polarized
LNA	Low Noise Amplifier
LO	Local Oscillator
MIR	Microwave Interferometric Reflectometer
Msps	Mega Samples Per Second
NED	North East Down
NF	Noise Figure
PARIS-IoD	PAssive Reflectometry and Interferometry System In-orbit Demonstration
PPS	Pulse Per Second
PRN	PseudoRandom Noise
Q	Quadrature phase component
RF	Radio Frequency
RFI	Radio Frequency Interference
RMS	Root Mean Square
RHCP	Right Hand Circular Polarized
SAW	Surface Acoustic Wave
SBAS	Satellite-Based Augmentation Systems
SDR	Software Defined Radio
SNR	Signal-to-Noise Ratio
$T_c$	Chip time of a PRN code
$T_{coh}$	Coherent integration time
$T_{code}$	PRN time length
USRP	Universal Software Radio Peripheral
VNA	Vector Network Analyzer
${\lambda }_{L1}$	Wavelength of GPS at L1 central frequency (19.04 cm)
${\lambda }_{L5}$	Wavelength of GPS at L5 central frequency (25.5 cm)