Radio Science

Rings of Saturn
A profile of the rings of Saturn derived from radio occultation at three wavelengths, corresponding to frequencies of three radios on the Cassini spacecraft: S-band (red), X-band (green) and Ka-band (blue). The signal extinction is visible in this image, from which the optical thickness and particle size distribution can be inferred. The profile is superimposed on an image of the rings generated from radio occultation data (credit: E. A. Marouf, SJSU).
 

Radio links between spacecraft and Earth are utilized to examine changes in the characteristics of electromagnetic waves, such as their phase/frequency, amplitude, radio spectrum, or polarization, to investigate many aspects of planetary science, space physics and fundamental physics.

 


Selected Research Areas

 

Radio Occultations

A planetary body’s atmospheric composition, temperature, pressure, and ionospheric composition can be determined by tracking a spacecraft as it passes behind it.

As a spacecraft’s signal propagates through a ring system, it can reveal information on the particle size and distribution of the rings.

Some recent opportunities and discoveries achieved using radio occultation:

  • Recent atmospheric characteristics of Mars from MRO (2014)
  • The Ionosphere of Saturn observed by the Radio Science System (2014)
  • The Structure of Titan’s atmosphere from Cassini Radio Occultations (2012)
  • Demonstration of Mars crosslink occultation (2015)

 

Saturn

 

Gravity Field Determination & Celestial Mechanics

Careful tracking of the Doppler shift of a spacecraft's radio transmissions yields information about planetary gravitational fields, shapes, masses, and ephemerides.

Recent opportunities and discoveries:

 

Jupiter

 

Bistatic Scattering

This technique uses a spacecraft's antenna to point at a specific point on a planetary body (called the specular reflection point). The the reflected signal is received at the Deep Space Network, and is analyzed to reveal details about the roughness and composition of the surface.

Recent opportunities and discoveries:

 

Scattering

 

Doppler Wind Experiments

During the descent of a probe into a planetary atmosphere, the wind affects its trajectory, causing a Doppler shift on the transmitted signal. This effect can be detected by the Deep Space Network on Earth. Analysis of the received data reveals the wind speed and direction in the atmosphere at the probe's location.

Recent opportunities and discoveries:

  • Huygens Probe Doppler Wind Experiment (2002)
  • Galileo Probe Doppler Wind Experiment (1998)

 

Doppler experiment

 

Solar Corona Characterization

As a spacecraft passes near the Sun during solar conjunction, the transmitted signal is altered by charged particles emitted from the solar corona. An analysis of electron content in the received signal can help characterize the solar corona.

 

 

Solar corona characterization

 

Tests of Fundamental Physics

Some spacecraft have radio equipment sensitive enough to enable the search for gravitational waves. This data can provide validation of the Theory of Relativity through estimation of post-Newtonian parameters using relativistic time-delay.

Recent opportunities and discoveries:

 

Fundamental physics test

 

Critical Events, Engineering & Research

At JPL, the Raio Science Systems Group also supports mission critical events, such as Entry, Descent, and Landing (EDL), orbit insertion, and spacecraft launch and recovery, looking for changes in the signal transmitted to determine the state of the spacecraft.

Recent opportunities and discoveries:

  • Sleuthing MSL EDL performance from the X-band carrier (2013)
  • Analyzing Optical Ranging Measurements from the LRO spacecraft (2016)
  • Signal detection during Juno Jupiter Orbit Insertion (2016)

 

Critical events