Launched from Cape Canaveral Air Force Station on August 5, 2011, Juno is NASA’s second spacecraft created under New Frontiers Program (the first being Pluto New Horizons mission) and currently on the way to the gas giant planet Jupiter. Juno spacecraft is due to arrive on Jupiter on July 4, 2016, and NASA expects it to accomplish its primary goal of improving understanding of the origin and evolution of Jupiter as well as the solar system.
In October 2013 – after being in space for two years – Juno spacecraft swung past the Earth, with closest approach being within 350 miles of Earth’s surface. It completed a maneuver called gravity assist in which Juno used Earth’s gravity to boost its speed toward Jupiter.
Juno spacecraft will travel a total distance of about 1.74 billion miles (2.8 billion km) before reaching Jupiter’s orbit. It will be the second spacecraft – after Galileo probe – to orbit Jupiter. Galileo had orbited Jupiter from 1995-2003.
After it arrives on Jupiter, Juno will be put in a polar orbit to examine the composition, polar magnetosphere, magnetic field, and gravity field of the planet. The spacecraft will seek for clues about the formation of Jupiter, including distribution of mass, presence of a rocky core, and deep winds which can attain speeds of 384 miles per hour. The spacecraft will orbit Jupiter 37 times in next 20 months. During this period, the microwave and infrared instruments on board Juno will measure the thermal radiation originating from deep within Jupiter’s atmosphere. The spacecraft will also study the convection that drives circulation patterns in the atmosphere of Jupiter, and also analyze its polar magnetosphere and gravitational field.
Juno is equipped with three solar arrays wings to give power to this spacecraft, and also stabilize it. Solar arrays are generally used with spacecrafts working in the inner solar system, such as satellites orbiting Earth. For missions to outer solar system, radioisotope thermoelectric generators are generally used. Solar array wings deployed on NASA’s Juno spacecraft are the largest ever used for a planetary probe.
The Juno mission is being managed by the Jet Propulsion Laboratory – a division of the California Institute of Technology in Pasadena. The principal investigator of the mission is Scott Bolton of the Southwest Research Institute in San Antonio, Texas, while co-investigators include Andrew Ingersoll of California Institute of Technology, Toby Owen of the University of Hawaii, Candy Hansen of the Planetary Science Institute, and Frances Bagenal of the University of Colorado at Boulder. The development and construction of Juno spacecraft was completed by the Lockheed Martin Corporation.
The velocity of Juno spacecraft is approximately 51,000 miles per hour relative to Earth, 12,000 miles per hour relative to Jupiter, and about 16,000 miles per hour relative to the Sun. On Feb. 19, 2016, Juno was about 413 million miles (665 million kilometers) from Earth. A radio signal sent from Earth took about 37 minutes to reach Juno.
The planned elliptical polar orbit of Juno spacecraft will enable it going closer to the poles – within 2,672 miles (4,300 kilometers). Each orbit will take 4 day to complete and will help Juno avoid any long-term contact with Jupiter’s radiation belts.
The Juno mission will conclude in February 2018.
The scientific objectives to be achieved by Juno spacecraft’s suite of science instruments include:
- To study Jupiter’s atmosphere and to measure the atmospheric composition, temperature, cloud motions, cloud opacity, and other properties.
- To determine the ratio of oxygen to hydrogen and to measure how much water is present in Jupiter’s atmosphere.
- Estimating Jupiter’s core mass.
- Mapping gravitational field of Jupiter and to analyze the distribution of mass in the interior of this planet.
- Mapping Jupiter’s magnetic field, analyze its origin and structure, and assess how deep in Jupiter is the magnetic field created.
- Characterizing the 3-D structure of Jupiter’s polar magnetosphere, especially the auroras.
- To provide new insights about how huge magnetic force field of Jupiter affects its atmosphere.
NASA’s Juno spacecraft is carrying with it a suite of scientific instruments. These are:
Jovian Auroral Distribution Experiment
Jovian Auroral Distribution Experiment (JADE) is an energetic particle detector placed on board Juno to measure the energy, angular distribution, and the velocity vector of electrons and ions at low energy in the aurora of Jupiter. JADE has electron analyzers mounted on three sides of the upper plate to measure frequencies three times higher than those measured by the Jovian Energetic Particle Detector Instrument.
Jovian Energetic Particle Detector Instrument
Jovian Energetic Particle Detector Instrument (JEDI) will be used to measure the velocity vector and angular distribution of electrons and ions at high energy (electrons from 40 keV to 500 keV and ions between 20 keV and 1000 keV) present in Jupiter’s polar magnetosphere. Three identical sensors in JEDI will study only particular ions of helium, hydrogen, sulfur and oxygen.
Jovian Infrared Auroral Mapper
Jovian Infrared Auroral Mapper (JIRAM) is a spectrometer mapper that will carry out surveys in the upper layers of Jupiter’s atmosphere – about 50 and 70 km deep (with pressure in the range 5 to 7 bars). While operating in the near infrared range, between 2 and 5 μm, JIRAM will capture images of the aurora in regions where H3+ ions are in abundance. This instrument will also measure the heat radiated by the atmosphere to determine how clouds with water flow beneath the surface. The device will also detect presence of water vapor, methane, phosphine and ammonia in the atmosphere of Jupiter.
The magnetometer on board Juno spacecraft will conduct magnetic field investigations, including magnetic field mapping, determining the 3-D structure of the polar magnetosphere, and analyzing the dynamics of Jupiter’s interior. The Flux Gate Magnetometer (FGM) experiment will focus on measurement of strength as well as the direction of the magnetic field lines, while the Advanced Stellar Compass (ASC) experiment will look at the orientation of the magnetometer sensors.
The microwave radiometer (MWR) consists of six antennas to measure electromagnetic waves with frequencies in the microwave range, that is, 600 MHz, 1.2 GHz, 2.4 GHz, 4.8 GHz, 9.6 GHz and 22 GHz. MWR will also try to measure the amount of water and ammonia in the deep layers of the Jupiter’s atmosphere – 500 to 600 km deep (up to 200 bar pressure). The data obtained with MWR will help find out the depth at which atmospheric circulation on Jupiter exists.
The Gravity Science instrument will make use of radio waves to create a map of the distribution of mass inside Jupiter. Scientists believe Jupiter has an uneven distribution of mass which results in small variations in gravity all along the orbit. Variations in gravity will cause small changes in the velocity of the probe, which will be monitored by the Gravity Science probe when it runs closer to the surface of the planet.
JunoCam is a visible-light color camera/telescope that will function only during first seven orbits around Jupiter. After that, it will become dysfunctional because of the damaging radiation and magnetic field of the planet. This camera will invite the public to serve as a virtual imaging team.
Radio and Plasma Wave Sensor
The main function of Radio and Plasma Wave Sensor will be to measure the radio and plasma spectra in the auroral regions in Jupiter.
Ultraviolet Imaging Spectrograph
The Ultraviolet Imaging Spectrograph (UVS) will analyze the position, wavelength, and arrival time of detected ultraviolet photons on Jupiter. This instrument will also provide spectral images of the ultraviolet auroral emissions in Jupiter’s polar magnetosphere.