Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.cosmos.ru/conf/2009elw/presentations/presentations_pdf/session2/gurwitz_ELW.pdf Äàòà èçìåíåíèÿ: Mon Mar 2 19:59:32 2009 Äàòà èíäåêñèðîâàíèÿ: Mon Apr 6 23:51:47 2009 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: m 8

Planetary Radio Interferometry and Doppler Experiment (PRIDE) for a Europa-Jupiter mission

Leonid Gurvits, Sergei Pogrebenko, Peter Fridman, Giuseppe Cimo JIVE, Dwingeloo, The Netherlands
Europa Lander: Science Goals and Experiments IKI, Moscow, Russia, 10-13 February 2009


Generic PRIDE configuration
Background radio sources

Earth
VLBI Network and Two-way tracking stations

Orbiter

Planet-target
Micro Lander Balloon

PRIDE utlises and enhances generic instrumental configuration of the mission

Venus
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PRIDE-EJ: multi-target multi-purpose experiment

PRIDE-EJ TRL : just great
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PRIDE: Earth-based segment

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Huygens VLBI heritage, 2005
x v
x v

= 1 km = 1 km = 3 cm/s = 3 cm/s

· Ad hoc use of the Huygens "uplink" carrier signal at 2040 MHz · Utilised 17 Earth-based radio telescopes · Non-optimal parameters of the experiment (not planned originally) · Achieved 1 km accuracy of Probe's descent trajectory determination
09:30 UTC 16:00 UTC

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VEX Doppler tracking demo

· · · ·

ESA's Venus Express carrier spectrum, Metsahovi observation, New S/W spectrometer 0.6 mHz spectral resolution
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Science case for PRIDE-EJ
· Direct characterisation of the orbiter and probe(s) signal by means of "VLBI tracking" and radial Doppler measurements · VLBI estimates of the probe(s) state vector (lateral coordinates)
· Tidal deformations/seismology of Europa (X- or Ka-band) · Gravimetry · Input to the fundamental physics package (see Odyssey ESA CV proposal)

· Radio occultation observations (Jovian magneto-/iono-sphere) · "Cruise" science plus mission diagnostics ("health check") · High degree of synergy with in situ measurements · Complementary to DeltaDOR measurements plus · Direct radio link with a small (Europa) probe (lander? penetrator?) as the case for SKA at S- or X-band(s)?

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PRIDE-EJ versus Huygens VLBI tracking
Huygens Radio link frequency Distance VLBI "fringe" SNR 2 GHz 8 AU 10 - 30 PRIDE-EJ 2/8/32 GHz ~5 AU 30 - 100 Resolution gain 1/4/16 1.5 ~3

Linear resolution (1)

1 km

240/50/13 m

~5/18/75

· · ·

Conservative estimate, today's technology (TRL>8) Minimal special requirements for the on-board instrumentation In-beam "Orbiter-Probe" calibration can improve SNR further

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Instrumental requirements of PRIDE-EJ
· Earth-based segment:
· A global network of radio telescopes and tracking stations; · (Mission-adjusted) data processing centre · Logistical network

· Onboard segment (all probes/spacecraft of the mission):
· Multi-frequency transmitters and related instrumentation (antennas etc.) · Stable Local Oscillator (LO)

All required technologies are mature and verified! · However:
· Demo/preparatory experiments are desirable (and in fact being planned) · Multi-target multi-frequency mode can be verified using e.g. Mars probes/orbiters (helps to calibrate/mitigate propagation effects)
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Astronomy of the XXI century
radio SKA mm and submm ALMA



JWST infra-red optical X-ray XEUS/IXO ELT

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SKA Science Science
· Science case developed over ~10 yr by international group of astronomers and physicists · Published as special issue of New Astronomy Reviews · Five Key Science Projects (KSPs)
1. 2. 3. 4. Probing the Dark Ages Galaxy Evolution, Cosmology, & Dark Energy The Origin & Evolution of Cosmic Magnetism Strong Field Tests of Gravity Using Pulsars and Black Holes 5. The Cradle of Life/Astrobiology

... plus The Exploration of the Unknown as an underlying philosophy for design and costing
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90 years of radio astronomy

and the Discovery exponent

SKA

Global Radio Wavelength Observatory:
SKA-lo: > 0.5 metre SKA-mid: 1 m < <~ 3 cm SKA-hi: 6 cm < < 1 cm

QuickTimeTM and a TIFF (Uncompressed) decompressor are needed to see this picture.

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Square Kilometre Array (SKA) as a DtE facility
· Sensitivity gain over a large DSN-style antenna >100 · Frequency range: 0.3 ­ 20 GHz · Prime goal: superior L-band sensitivity · Fully operational in 2020; high operational readiness from 2018 · Multi-user (multi-field/multibeam) functionality

SKA collecting area = 100 x VLA

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SKA Reference Design and possible locations

More info at: www.skatelescope.org
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Bit-error rate for EJSM-SKA DtE

BPSK

BPSK + error control coding

32-ary orthogonal Coherent modulation

30­50 bps with ~10-4 ­ 10-3 BER achievable Omnidirectional transmission, 1 ­ 3 W
Further details: Fridman et al., 2008, SKA Memo No. 104
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PRIDE-JE summary and actions
· VLBI tracking of any EJSM S/C at 2 and/or 8 GHz is feasible; 2D lateral positional accuracy of >~100 m is achievable · Trade-offs need to be addressed NOW (at least in preliminary terms)! · VLBI tracking of the Jupiter orbiters at 8 and 32 GHz is feasible · VLBI-based Radial Doppler measurements of the Europa lander at X-band would enable factor of 10-50 improvement over Huygens · Backup DtE of Europa lander signal with 30­100 bps at S- or Xband can be addressed ­ requires "injection" into the SKA design study Questions: · Is there a need for a higher positional accuracy? · How many targets PRIDE-JE deal with: orbiter, lander(s)?
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Hunting for water masers in Saturnian system
Pogrebenko et al. 2009, A&A 494, L1
Antenna beam coverage MC-32 MH-14

· Observations started in 2006 using Huygens software correlator for Mk5A data processing. · More than 300 hours of observation collected in 2006 ­ 2008 with MC and MH telescopes. · HW spectrometer MSpec0 at Medicina. Medicina 32m, IT · Software spectrometer was developed for Metsahovi. · Data analysis @ JIVE. Metsahovi 14m, FI


Orbital phases observed Hyperion

Sponge-like shape of Hyperion might be a result of a selective sublimation of ice, enhanced by interaction with Solar wind when the satellite is outside the Kronian magnetosphere.

Titan

Magnetospheric bow shock

When outside thy magnetosphere, Hyperion is about there

Titan's neutral torus

Titan has a lot of gases in its exosphere to provide collisional pumping for trapped water molecules.

Magnetosphere of Saturn


Enceladus

Water-water collisions dominated pumping ? Presence of low energy electrons can also help (Elitzur & Fuqua 1989)
Chemical composition of the "plume"

Electron density in Saturn environment
Schippers et al, 2008

Waite et al, 2008

Possibility to compare astrophysical models with in situ measurements
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Orbital phase from which the emission was detected is indicated by red

Persistence check: spectra for 3 independent epochs compared

Atlas
Equatorial accretion ridge

Global average

Emission was detected not from Atlas itself, but associated with a spot lagging Atlas by few minutes along its orbit

F ring

A ring

F ring: quite an active