RADIO SCIENCE EXPERIMENTS OF JOINT OBSERVATION OF YH-1 AND PHOBOS-GRUNT

Jinsong Ping, YH-1 VLBI team & RS teamShanghai Astronomical Observatory, CAS

Nandan Rd. 80, 200030 Shanghaipjs@shao.ac.cn

The second Moscow Solar System Symposium (2M-S3)Moons of planets, IKI, Moscow, Oct.9-14, 2011

Df. Planetary Radio Science (RS)Science to investigate planetary atmosphere and ionosphere,

gravity, mass(GM), ring, ephemeris, solar wind, comets, gravitational wave and red shift…mainly by measuring the change of phase , amplitude, polarization of the radio signal from S/C to ground station, which includes:

• Mass and gravity of planets and the moons；• Atmosphere: pressure, temperature, contents；• Ionosphere: electron density, corona, interplanetary media；• Testing experiments of general relativity;• Orbit and rotation of the planets and moons；• Unification of celestial reference frames;• Planetary surface by bi-static radar mode.

Ref: Gavrik; Duev; Rosenblatt; Smirnov; Kosov; this meeting

Power Spectra of Mars Gravity ModelUsing DSN radio matrix data

GGM1

GGM2b

SHAOSolution

Mars Gravity Model fromMGS tracking data

EXAMPLE01

Chinese VLBI Network For S/C POD Tracking

Coverage:EW34° SN18°Baseline length:1115km to 3249km

MARK5B& CVSRReceivers;S/X/Ka

EXAMPLE02

CE-1 Tracking Data CoverageOn CLTM-s01 topography model

Planetary Gravity: Improving Lunar Gravity by CE-1 Missions

Gravity Error Spectral

CEGM is 2 times better at low orders/degrees

LP100k

SGM100h

CEGM50c

Lunar DEM is improved by ~20meter with VLBI + RR&R POD data

MEX Open-loop RO

mexmrs_0022, mexmrs_0024,

EXAMPLE03

EXAMPLE04 a joint bi-static radar study by SHAO and JIVE

Applications RS in Chinese Martian exploration project YH-1 YH-1 will be YH-1 will be launched with Phobos-soil in November, 2011

Mission:1.YH-1 will explore Martian space environment by in situ measurement

and occultation with Phobos-Soil. A free-fly orbiter…2.Two-point measurement will provide deep inside view of Martian space

environment.3.Only 1-way open-loop tracking and OD for YH-1 S/C

Scientific Objectives

1 To study in details of Martian space magnetoshpere, ionosphere and the plasma distribution and its variations

- FGM, Plasma package, UHF receiver

2 To study Martian ions escape mechanism- Plasma package

4 To explore the Martian gravity field near equator - VLBI

3 To have a moderate survey of Martian surface topography and sandstorms

– Visible light camera

Main Technical Specification

Mass ~110kg

Body size 750mm×750mm×600mm

Power on orbit operation

Long term ： 150WShort term ： 200W

Orbit

Type ： ellipse orbitInclination ： 23 ～ 25°Apoapsis ： 400 ～ 1000kmPeriapsis ： 74000 ～ 80000km

Attitude control Zero momentum three axis stabilization

Electrical powerRegulated busSolar array, 4.674m2 ,triple junction GaAs cells Lithium ion batteries 30AH

TT&C X band ， CCSDS standard

On-board computer 31750CPU

Thermal control Passive control

Reliability 0.65 （ EOL）Lifetime 1a

Introduction of the YH-1 mission situation

Testing in 2008 & 2010:

craning for measurement center of gravity vibration test

Joint Russa-China Martion Missions:Phobos-Grunt & Yinghuo-1 (YH-1) after Zelenyi , this session

YH-1 &PGSC same beam VLBI observation to cancel Earth atm&iono effects, will success the single S/C RS observation in the joint missions.

MARS

Orbiter

Phobos (Lander)

VLBI-2VLBI-1

1-way Doppler and D-VLBI only are used for OD and POD of YH-1 X-band 8.4GHz CWs are used.

Earth Atm & Iono

Simple & Easy

•Onboard USO/clock is stable enough;•Advanced Software Radio Tech;•Save transferring time and resource

Open Loop Tracking follow DLR-LP-1998

USO StabilityFor FGSC & YH-1

YH-1 is using a pair of USOs with long-term stability of 7x10E-11, may be improved by 1 order; 1x10E-12 for short term stability, same as FGSC

VLBI/CAS is powerful for deepspace S/C open-loop OD

MEX OD ability test by new developed RSR of CVN4ch, VLBI recording, RSR, Doppler & Phase retrieving

北京中心火星探测定器轨软件研制进展及精度初步分析Based on OD and POD, the GM andlow order/degree gravity for Marsand Phobos will be expected to be estimated and improved by the joint missions

Mars gravity variation:

Follow Konopliv, JPL/NASA

Working mode of bi-static radar to study Martian and Phobos surface characteristics

a

asym ptotes

r0

Earth

S /C

a

vE

vS

Venus (r)

Planetary RO in Phobos-Grunt & YH-1 missions is possible to observe the day time and night time profiles of atm/iono at low latitude

Doppler Freq

Reflection and Altitude

S/C-Planet-SiteInformation

Abel Transfer

Atm. Model

Electron Profile Atm. Density Profile

Atm. Pressure Proflie

Temperture Proflie

大气组成

静流体平衡

状态方程

行星大气无线电掩星观测数据解析流程框图

VLBI Experiment Objectivesin YH-1 & Phobos-Grunt mission

•To do OD and POD for YH-1 mission;

•To define more exactly Sun system’s parameters (Astronomical constant like GM and others, orbital parameters of Mars and Fobos);

•To study the Martian ionosphere using RS method;

•To study the Martian surface using bi-static radar method;

•To define more exactly limits of variation of universal gravitational constant;

•To define more exactly geometrical tie of dynamical coordinate system having original in Sun system mass centre of with coordinate system based on quasar angular coordinate measurements.

Also, following information of Phobos will be recovered

by this joint mission:1 ） Density by combining MEX figure with GM

2) Inner structure…ice or empty ?

3) Rotation/liberation (Main liberation with possible periods of ~24.6h, 12.3h, 7.55h, 3.78h, 184.3h, 92.2h, 38.2h, 19.1h need to measure.)

4) Orbit & Orbit evolution

Thank you