Mission Objectives

NASA’s main goal was to understand the origin and evolution of our solar system. Visiting Ceres and Vesta was crucial for this as these protoplanets were some of the earliest objects to form alongside other planets. The three major scientific objectives for the mission were:

1. Capture the earliest moments in the origin of solar systems and realize the conditions under which these objects formed.

2. Determine the nature of building blocks of planets to improve our understanding of the formation of terrestrial planets.

3. To gauge the difference between Ceres and Vesta which followed different evolutionary paths to understand what parameters control that evolution.

Mission Timeline
Launch	27th September 2007
Mars Gravity Assist	17th February 2009
Arrival at Vesta	16th July 2011
Departure from Vesta	5th September 2012
Arrival at Ceres	5th March 2015
End of prime mission	June 2016
Start of 1st extended mission	July 2016
Start of 2nd extended mission	October 2017
End of Mission	1st November 2018

Dawn Spacecraft 

Solar Arrays: Solar arrays are 8.3 meters long and 2.3 meters wide each. On these arrays are 11480 individual photovoltaic cells which can convert 28% of solar energy it receives into electrical energy. These arrays had a gimbaled connection which allowed them to rotate any desired angle to face the Sun.  

Antennas: Dawn had 2 types of antennas onboard, for communication with the earth through NASA’s Deep Space Network. And only one of those could be used at a time. It had 1 Large 1.52-meter diameter parabolic High-Gain antenna and three low gain antennas for when the spacecraft was not pointing high-gain antenna towards Earth.

Science Payload 

1. Framing Camera: FC mapped Vesta and Ceres through the clear filter and 7 bandpass filters allowing the wavelengths from visible to near-infrared. The camera was used for understanding surface geomorphology and physical parameters of the asteroids as well as for orbit navigation. 

2. Visible and Infrared spectrometer: VIR spectrometer consisted of 3 modules Optical system, proximity electronics, and cryocooler. It could see from 0.3 to 5 microns covering near-ultraviolet, visible and infrared regions of the spectrum.  

3. Gamma Ray and Neutron Detector: The instrument allowed spacecraft to measure the elemental composition of Ceres and Vesta. A total of 21 sensors with a wide field of view was used to detect energy from gamma rays and neutrons that were reflected or emitted by celestial bodies. It could reveal atomic constituents of the surface of Ceres and Vesta down to the depth of 1 meter.

Ion Propulsion

Dawn spacecraft has three 41-centimeter-diameter ion thrust units(8.9 kg each) which are movable in two axes to control spacecraft attitude. Two of these thrusters were necessary to complete the mission but a third one was carried as a spare. These thrusters work by using an electrical charge to accelerate ions from xenon fuel up to a maximum rate of 3.25 milligrams per second. 

The Dawn carried 425 kg of xenon propellant at launch and was stored in a compact form(1.5 times denser than water at launch) onboard the spacecraft. ‘Xenon’ was selected as propellant due to its chemical inertness and the atoms are relatively heavier compared to other propellants which help provide larger thrust. At max. Thrust, each engine is capable of producing 91 millinewtons - almost the same amount of force with which we can hold a piece of notebook paper in our hands.

Dawn Spacecraft Earth Orbit Mars Orbit Vesta orbit Ceres Orbit

Key Facts

• Dawn is the first spacecraft to orbit two destinations in space. 

• The record powered flight: Ion propulsion was active for 5.9 years(54% of the time in space as of 7th Sept 2018).

• Dawn was able to travel to 2 destinations for the price of one by using Ion-engine technology. 

• Dawn's mission is the first to orbit a main-belt asteroid and the first to reach a dwarf planet.

The Spacecraft Construction

Three separate booms were attached to the central decahedral bus. A 3.66 m diameter(Parabolic) high-gain antenna was mounted on top of this Bus. 

1. Science boom: Extending out 2.5 m from the bus, had Steerable scan platform with imaging and spectroscopic remote sensing instruments at the end. Plasma and charged particle detectors were placed at various distances along this boom. 

2. Magnetometer boom: A separate 13 m. long boom opposite to Science boom had Magnetometers.

3. Generator boom: A third boom extending down and away from the science boom holding the power source of the spacecraft(RTGs).

Two whip antennas (10 m each) also extended from the spacecraft for plasma wave and planetary radio astronomy investigations.

The Power source 

Plutonium oxide generated heat as it decayed and a bimetallic thermoelectric device was used to convert this heat into electric energy for spacecraft instruments. The initial output of the RTGs was 470 W of 30 V DC power at launch but it kept decreasing as more Radioactive material was expended.

Mission Timeline

Launch: Sept. 5 1997 from Cape Canaveral, Florida onboard Titan IIIE-Centaur launch system. With a primary mission of exploring Jupiter and Saturn. 

Exploration of Jovian system: The closest encounter(280,000 km) of Voyager 1 to planet Jupiter was on March 2, 1979, but the imaging of Jovian system had already started in April 1978. At the beginning of January 30, 1979, Voyager took pictures of Jupiter every 96 seconds for a total of 100 hours allowing us to generate colour timelapse of 10 rotations of Jupiter.

Voyager 1 also captured incredible images of several of Jupiter’s moons during the flyby: Amalthea (420,200-kilometer range), Io (21,000 kilometers), Europa (733,760 kilometers), Ganymede (114,710 kilometers), Callisto (126,400 kilometers) and also discovered two new moons: Thebe and Metis.

The spacecraft made two course corrections after encountering the Jovian system to move to the Saturn system one of which was on April 9, 1979. And the second on Oct 10, 1979, was specifically for avoiding its trajectory to hit the Titan.

Exploration of Saturn System: The closest approach to planet Saturn was on Nov. 12 1980 within a range of about 126,000 km. During this, Voyager 1 found 5 new moons around the planet and also thousands of bands in the rings of the planet with shepherd moons which keep the rings well-defined.

It also photographed moons of Saturn: Titan, Mimas, Enceladus, Tethys, Dione, and Rhea. with the close approach to Titan at around 4000 km on November 12, 1979. Which revealed incredible details about the moon with a thick atmosphere and a possibility of liquid existing on the surface.

Boundaries of Solar System: The planetary encounters were over after a visit to Saturn’s system, and Voyager 1 was set on a trajectory to leave our solar system with a speed of about 523 million km per year(59,703 km/hr). On December 16, 2004, spacecraft showed an indication of crossing the termination shock and entering into the Heliosheath. And it finally exited the solar system on August 25, 2012, and set the record for human-made spacecraft to ever leave the Solar system. 

Before this record, on February 14, 1990, Voyager 1’s cameras were pointed Backwards to take the first ‘Selfie’ of our Solar System from a distance of 6 billion km(40 Astronomical Unit) from the Sun. The image was later known as ‘Solar System Family Portrait’ with no Mercury as it was too close to Saturn and only the dark side of Mars was visible.

Key Facts

• On February 17, 1998, Voyager 1 overtook Pioneer 10 at a distance of 69.4 AU from the Sun to become the most distant object sent into space by humans. 

• Voyager 1 was launched 16 days after the launch of Voyager 2 but it was on a faster route and overtook Voyager 2 on December 15, 1977.

Launched aboard space shuttle columbia from Kennedy Space Center on 23rd July 1999, The Observatory is named after a Nobel Prize winner, Indian-American astrophysicist Subrahmanyan Chandrasekhar. The telescope is specifically designed to observe the X-Ray sources in the universes such as Galaxy clusters, exploded Stars, and matter around Black Hole. 

Chandra Specifications