The Saturn Orbiter: Cassini LAKSHMI SRAVANTHI KOUTHA

OUTLINE Timeline of Cassini Objectives Instruments on board Findings Cassini RADAR Modes of operation SAR mode Mapping the Titan Specs and range resolution Communication with Earth NASA Deep Space Network References

CASSINI - HUYGENS Joint Mission By NASA, ESA and ASI. TIME-LINE:- Idea proposed: 1982 Launch: October, 1997 First Venus gravity assist: April 1998 Second Venus gravity assist: June 1999 Earth gravity assist: August 1999 Jupiter gravity assist: December 2000 Arrive at Saturn and Saturn orbit insertion: July 1, 2004 Release of Huygens Probe on Titan: December 25, 2004

TIME-LINE AND ORBIT

OBJECTIVES Behavior of the Saturn Rings and their origin Number of moons Find about the heat emitted by Saturn Dark material on Iapetus Source of methane on Titan Does Titan have solid surface? More study about Enceladus Mass and age of particles in Saturn rings Mass of the moonsSources of lightning on Saturn Figure out if Rhea has it's own ring Find Saturn's rotation rate and it's internal structure

ORBITS MADE BY CASSINI

INSTRUMENTS ON-BOARD CASSINI Composite Infrared Spectrometer Imaging Science Subsystem Ultraviolet Imaging Spectrograph Visible and Infrared Mapping Spectrometer Cassini Plasma Spectrometer Cosmic Dust Analyzer Ion and Neutral Mass Spectrometer Magnetometer Magnetospheric Imaging Instrument Radio and Plasma Wave Science Cassini RadarRadio Science

FINDINGS ON CASSINI Huygens probe landing on Titan First outer space landing ever Had only 3 hours of battery life Titan looked similar to Earth before evolution Hydrocarbon atmosphere Titan surface captured by Huygens probe (with different signal processing)

FINDINGS OF CASSINI Witness for the birth of a new Saturn moon Observed storm that is seen once in 30 years

FINDINGS OF CASSINI North pole hexagon of Saturn

FINDINGS OF CASSINI Tall vertical structures seen on the rings of Saturn Tiger stripes on Enceladus

FINDINGS OF CASSINI Liquid on Enceladus from reflections Earth like liquid bodies on Titan

FINDINGS OF CASSINI Details falsifying the previous assumptions made about Saturn Kilometric radiation

CASSINI RADAR

RADAR MODES OF OPERATION

SYNTHETIC APERTURE RADAR MODE G Hz Ku Band

SAR IMAGES

SPECIFICATION Altitude : Km Transmit Power : 65 W Chirp Bandwidth : MHz PRF : Hz Ground Range Resolution : Km Azimuth resolution : Km Incidence angle : 14 to 35.4 (degrees) SwathWidth : 68 to 311 Km Transmit path loss : 2 dB Receive path loss: 2.5 dBData rate : Kb/s

RANGE RESOLUTION Range resolution : c/ 2B sin t where c=speed of light B= chirp Bandwidth t = incidence angle B=850 KHz when altitude < 1600 Km =425 KHz when altitude is >1600 Km but < 4000 Km Incidence angle = degrees, altitude between 1000 and 1556 Km =16.4 to 28.9 degrees, altitude between 1556 and 2895 Km =22.2 to 35.4 degrees, altitude between 2895 and 4000 Km For B=850 KHz and t= 14 degrees Range resolution=729.45For B=425 KHz and t=35.4 degrees Range resolution = Range resolution lies in between 420 and 2700 m Proved to be in the range

COMMUNICATIONS WITH EARTH Now that data is acquired. This has to be sent back to Earth. But HOW?? NASA Deep Space Network

GOLDSTONE ANTENNA While the Cassini was taking gravity assists from Venus and Earth, it being near to the sun could cause damage to the spacecraft, so the HGA is used as shield rather than for communication.But going on in the long dark journey, the HGA is used for communication.

DATA RATES From data sheets the downlink data rate is about Kb/s In each flyby about 1 Gbit data is collected Transfering this 1 GB of data will take about Hours Data reveals that 4 GB/day is transferred from the spacecraft

REFERENCES C. Elachi,m.d. Allison,l. Borgarelli,p. Encrenaz, e. Im1, m. A. Janssen,w.t.k. Johnson,r.l. Kirk,r.d. Lorenz,j.i. Lunine, d. O. Muhleman,s.j. Ostro,g. Picard,f. Posa,c.g. Rapley, l. E. Roth, r. Seu,l.a. Soderblom,s. Vetrella, s. D. Wall, ∗, c. A. Wood and h. A. Zebker 'Radar: The Cassini Titan Radar Mapper ‘ wikipedia.org

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