Long wave planetary radar(LPR)

Subsurface radar sounding of the Fobos ground

N.A.Armand, V.M.Smirnov, V.N.Marchuk, O.V.Yushkova, Institute of Radioengineering and Electronics of RAS,

Moscow

V.V.Abramov, A.S.Bazhanov2

Special Design Bureau of IRE RUS, Fryazino, Russia.

The experiment purpose, expected results

Revealing of Phobos deep structure Estimation of in-situ rock density of

Phobos ground Research of a relief and roughness of

Phobos surface Estimation of dielectric properties of a

ground on different depths along a line of the spacecraft flight

THE PHYSICAL SCHEME OF EXPERIMENT

SC

Reflection of surface

Phobosstructure

Reflection of subsurface

layers

Layer 1

Layer 2

Layer 3

THE PHYSICAL SCHEME OF EXPERIMENT

Distance less then 1 km Distance higher then 1 km

The scheme of carrying out of survey sounding of a Phobos surface

by the radar LPR in a quasisynchronous orbit

MarsPhobos

Phobos orbit

Spacecraft orbit

Height 50 – 100km. Mode 1: 1 measurement per 90 seconds, 8191 sub pulses in a code keying signal

The scheme of survey sounding of a Phobos surface

The scheme of survey sounding of a Phobos surface

The scheme of carrying out of detailed sounding of a Phobos surface

by the radar LPR in a quasisynchronous orbit

L=vt

Spacecraft orbit

H=50 km

Phobos

surfa

ce

Height 50 – 60 km. Mode 2: 2 measurement per second, 2047 sub pulses in a code keying signal.

It is planed 6 sessions in 10 min durations.

The scheme of detailed sounding of a Phobos surface in a quasisynchronous orbit

The scheme of carrying out of sounding of a Phobos surface

by the radar LPR at spacecraft landing

Phobos surface

Mode 4

H=20 km

H=1 km

H=100 m

Mode 3

Height from 20 km to100 m. Two sessions duration for 10 minutes, on 2 measurements per second.

Mode 3 - 255 sub pulses in a signal. Mode 4 - a monoimpulse.

The scheme of a Phobos surface sounding at spacecraft landing

LPR outward appearance

Device LPR technical characteristicsCarrier frequency 150 MHzFrequency range 15025 MHzSpectrum band 43 MHzAmplification factor 110 – 120 dBRadio-frequency pulse duration 26,6 nsThe number of sub pulses in phase code keying

signal8191, 2047,

255Height range 0 – 100 kmThe permission on a vertical on the Rayleigh 2 mNominal target pulse capacity of the transmitter 20 25 W

Input signal power 510 mWAverage power consumption 7 WAntenna length 1350 mmOverall weight 3.5 kg

Main parameters of operating modes of the radar LPR

Operating mode

Height range,

km

The number of sub- pulses in a

signal

Signal duration, T

(μs)

Energy gain,dB

1 120 – 30 8191 220 39 (20)

2 60 – 10 2047 55 34 (17)

3 20 – 1 255 6.8 24 (12)

4 1.5– 0 1 26,710-3 0

Probing signal of device LPR and its spectrum

• Spectra of a device DPR signal: by a green line the spectrum of an individual radio impulse, dark blue – code keying signal of 2047 sub pulses is shown

• .

N

S(N)

Device LPR information capacity

Place of experimentOperating mode

Meassu-rement capacity, bytes

Operating time,

min

The number of meassu-rements

per session

The number of sessions

Operating mode

total capacity,

Mb

Quasi synchronous orbit

1 57024 180 120 4 26.1

Quasi synchronous orbit

2 16896 5 600 6 58.1

Landing (up tо 1 km)

3 4224 10 1200 1 4.8

Landing (lower 1 km)

4 2112 10 1200 1 2.4

Phobos surface 1,2,3,4 ≈20064 1*4 10 1*4 0.8

Total 92.1

Modeling of a LPR signal restoration (М=2047) at a signal to noise ratio -15dB is shown

N

N

U(N)

U(N)

Modeling of a LPR signal restoration (М=2047) at a signal to noise ratio -15dB is shown

N

N

U(N)

U(N)

Thanks for attention