Solar syaytem

Historic space missions to explore our Solar System

Take a tour on four of the historic space missions, designed to explore other planets of our Solar system.

Take a tour on four of the historic space missions, designed to explore other planets of our Solar system.


In Cassini- Huygens mission, NASA JPL along with European space agency (ESA) and Italian space agency (ISA) decided to launch a probe to the planet Saturn to study its rings and natural satellites. This mission involves Cassini probe and Huygens lander, which was the largest interplanetary spacecraft the Fourth probe that reached to the Saturn was Cassini, named after Italian astronomer Giovanni Cassini

Cassini launched in October 1997 and stayed on board for more than 20 years, out of which 13 years spent in orbiting Saturn and studying the planet and its system. Cassini spacecraft accompanied with comet rendezvous asteroid flyby (CRAF) spacecraft but due to a shortage of budgets, CRAF construction had terminated to continue the synthesis of Cassini. Main objectives of the Cassini mission includes:

  • To determine the 3D structure and dynamic behavior of the rings of Saturn.
  • To determine the composition of the surfaces of the various satellite
  • To measure the three-dimensional structure and dynamic behavior of the magnetosphere.
  • To explore the dynamic behavior of Saturn’s atmosphere at cloud level.
  • To Study the time variability of Titan’s clouds and hazes of planet Saturn.
File Photo: NASA
 Cassini- Huygens assembly

Cassini probe consists of computers, radio transmitter, attitude thrusters, reaction wheel, three radioisotope thermoelectric generators (RTGs), a high- gain and two low-gain antennas. Cassini orbiter also had 12 scientific instruments including: Composite Infrared Spectrometer (CIRS), Imaging Science Subsystem (ISS), Ultraviolet Imaging Spectrograph (UVIS), Visible and Infrared Mapping Spectrometer (VIMS), Cassini Plasma Spectrometer (CAPS), Cosmic Dust Analyzer (CDA), Ion and Neutral Mass Spectrometer (INMS), Magnetometer (MAG), Magnetospheric Imaging Instrument (MIMI), Radio and Plasma Wave Science (RPWS), Radar and Radio Science (RSS). 

Cassini flyby of Jupiter

Cassini probe undergoes two flybys of Venus on April 1998 and on June 1999. Upon its flyby of Jupiter, made its closest approach to the planet in December 2000 and captured more than 20000 images of Jupiter, its rings moons and marked some of the outstanding observations including dark oval of atmospheric haze and the size of the great red spot.
A close Flyby photograph of Jupiter captured by Cassini

Cassini flyby of Saturn

During Close flyby of Saturn, Cassini discovered 7 new moons orbiting Saturn, among them Three moons discovered in 2004, and four in later years during its flyby. Among them, the sixth moon identified within the G – ring, and Seventh in the A- ring of the Saturn’s unique ring system in the entire Solar system.
Cassini flew on to the moon Phoebe of Saturn on June 2004 and captured its first closest image
Moon Daphnis and phoebe moon captured by Cassini

Cassini made many other flybys of Saturns moons including Titan (2004), Enceladus (2005), Iapetus (2007), Rhea (2015), and Hyperion (2015), Dione (2015). In the Grand Finale mission, from April 2017 to September 2017, the probe made many close rounds around the Saturn for moving within its rings and when Cassini finally entered into the Saturn’ atmosphere, the mission controllers on earth mission announced an end to this historic probe and it crashed after colliding with Saturn’s surface. Though the mission has ended up, the analysis of the data will stay to continue for many years onward. 

Curiosity Rover

Curiosity rover is a car-sized rover, mainly constructed to explore Mars and to find out whether life is possible on the Red planet or not. The rover is a part of NASA‘s Mars Science Laboratory mission (MSL). It was launched on November 2011, landed on Mars on August 2012. The main MSL mission objectives include:

  • To identify the features that represent the effects of biological processes.  
  • To investigate the chemical, isotopic composition of the Martian surface.
  • To interpret the processes that have formed and modified rocks and soils
  • To search for the Martian atmospheric evolution processes. 
  • To determine the present state, distribution, and cycling of water and carbon dioxide on Mars.
  • To characterize the broad spectrum of surface radiations, including cosmic radiations and secondary neutrons. 

Curiosity is 2.9 m long, 2.7 m wide and 2.2 m in height and powered by Radioisotope thermoelectric generators (RTGs), with radioactive isotope Plutonium- 238. When this radioactive material decays, it emits heat that converted into electric voltage. Curiosity rover had four SPARC processor that ran the rover’s thrusters, Two PowerPC processors, Main processors that handled all the ground functions of the rover, and the fourth processor controlled the rover’s movements.
Rover also contains six wheels that are 50cm in diameter. Because of these wheels rover is capable of climbing huge dunes.

Curiosity was the fourth rover of NASA landed on the Martian surface since 1996. Though curiosity rover started work actively even when it only touches the planet’s surface at Aeolis Palus in the Crater Gale. It is believed that NASA Curiosity Rover can estimate the history of Mars up to two billion years old by the sediments from the Mars surface.
Gale Crater where Curiosity Rover landed

Voyager 1

A grand tour program to explore Solar system, which consists of two groups of robotic probes was proposed by NASA to study outer planets of the Solar system. After the first successful mission to Jupiter by Pioneer 10, the American space probe helped the Voyager’s engineers to develop Voyager 1 to deal with the intense radiation environment around Jupiter.

Initially, it was decided to be named as Mariner 11, a program included 10 mission in collaboration with NASA’s Jet propulsion laboratory to approach on Mars, Venus and Mercury in Solar system but due to a budget shortage, the mission restricted to only Jupiter and Saturn and renamed as Mariner Jupiter-Saturn probes. Later on, renamed as the voyager.

NASA launched Voyager-1 in Sep 1977, consisted of three-axis stabilization gyroscopes, 16 hydrazine thrusters and referencing instruments so that the probe’s radio antenna was able to point toward Earth. Its disabled systems included imaging science system (ISS).Radio science system (RSS). Infrared interferometer spectrometer (IRIS). Ultraviolet Spectrometer (UVS).

Planetary radio astronomy investigation (PRA). Active instruments included, Triaxial fluxgate magnetometer (MAG). Low energy charged particle instrument (LECP). Cosmic ray system (CRS). Plasma wave system (PWS). Defective instruments included, Plasma Spectrometer (PLS). Photo Polarimeter system (PPS).
Voyager 1 also has three radioisotope thermoelectric generators (RTGs) and each of which contains 24 pressed plutonium-238 oxide spheres.

 Like most of the probes, it also contained automatically operating cameras that were controlled by a computer command subsystem (CCS) which usually have a fixed computer program. The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft’s attitude or orientation to some reference frame. 

The planetary tour of Voyager 1 explored all the giant planets of the solar system including Jupiter, Saturn, Uranus, and Neptune, also discovered their 48 moons, the unique rings systems, and details about their magnetic effect

In the first flyby of Jupiter, the probe reaches the closest position to the planet in March 1979 and captured higher resolution photographs within 48 hours. For the very first time in history, a volcanic activity observed on the moon lo, which is the innermost of the four Galilean moons of the Jupiter.  

View of lava flows radiating from the volcano Ra Patera on Io
Sulfur rich lava flows from a volcano on Jupiter’s moon LO

 In the flyby of Saturn, the closest approach to the planet occurs on November 1980. The probe found that about 7% of the uppermost surface of Saturn contains helium gas while the rest contains hydrogen gas. 

Later on, in 2013, NASA confirmed that the Voyager 1 had reached the interstellar medium beyond Solar system and further predicted that by 2025- 2030, the probe will not be able to power even a single instrument.    

Voyager 2

NASA designed two groups of probes for grand tour mission, out of which one was voyager 2. One group was for exploring Jupiter, Saturn, and Pluto and the other was for Jupiter, Uranus, and Neptune. Voyager 2 launched in August 1977, 16 days before the launch of Voyager 1.

Voyager 2 contained 16 hydrazine thrusters, three-axis stabilizationgyroscopes and celestial referencing instruments which was a sun sensor, to point the antenna toward Earth. These all are part of the Attitude and Articulation Control Subsystem (AACS). It also included 11 scientific instruments to study celestial objects as it traveled through space.

Its disabled systems included imaging science system (ISS), Radio science system (RSS), Infrared interferometer spectrometer (IRIS), Ultraviolet spectrometer (UVS), Photo Polarimeter system (PPS),  Planetary radio astronomy investigation (PRA). Active instruments included Triaxial fluxgate magnetometer (MAG), Plasma Spectrometer (PLS), Low energy charged particle instrument (LECP), Cosmic ray system (CRS). Partially disabled instruments included Plasma wave system (PWS).
Voyager 2 contains 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres.

In the flyby of Jupiter, the probe reaches to the closest of the planet in July 1979 and captured photographs and also of the four Galilean moons including Europa, Callisto, Amalthea, Ganymede, and Lo, where Voyager-1 was first observed a volcanic activity.  

To Saturn, the closest approach to the planet occurred on August 1981. During these missions, it was found that at the uppermost pressure levels Saturn’s temperature was −203 °C, and at the deepest levels temperature increased to −130 °C. After the flyby of Saturn was completed the voyager 2 locked for some time, then the mission was extended to Uranus and Neptune.  

Moreover, the closest approach to Uranus and Neptune occurred on January 1986 and August respectively. During the flyby to Uranus, 11 moons discovered on Uranus and the probe examined its atmosphere and the ring system. Two unknown Uranian rings discovered by Voyager 2.

Voyager 2 image of Neptune
Planet Neptune captured by Voyager-2

In 2006, the international astronomical union confirmed Pluto as a dwarf planet. Later on, it was predicted that 2025 or slightly afterward no single instruments were powered by the probe.

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