Robotic Missions in Sun-Earth Space - Nasa's Science Goals, Nasa's Explorer Program, Nasa's Discovery Program

The Universe is an explosive, energetic and continually changing place.

—NASA

Sending humans into space is expensive and risky. It takes great resources to protect them and sustain them every time they leave the planet. Losing a crewed spacecraft means loss of lives. This is a high price to pay to learn about the universe. This explains why robotic spacecraft are so vital to space science. Since the beginning of the space age, satellites and probes have been sent out to gather data about Earth's surroundings. The earliest ones were rather crude in their technology. People referred to them simply as unmanned spacecraft. Times changed, and technology improved significantly. Today these mechanized explorers are called robotic spacecraft.

Only a handful of robotic spacecraft are sent to other planets. The vast majority of them circle the Earth or the Sun. Spacecraft in Earth orbit serve commercial, military, and scientific purposes. Scientists rely on satellites to collect data about Earth's weather, climate, atmospheric conditions, sea levels, ocean circulation, and gravitational and electromagnetic fields. These satellites are not space explorers but Earth observers that reside in space.

Other satellites in Earth orbit look outward toward the cosmos. These space observatories carry high-powered telescopes that beam images back to Earth. They can detect the light and radiation of celestial objects hidden from human view. They peer into the deep, dark regions of space to explore what is out there. Scientists use the images sent back from such satellites to learn about the origins of stars and planets and unravel some of the mysteries of the universe.

Closer to Earth is our own star, the Sun. It emits radiation and heat and produces a flow of energetic particles called the solar wind that constantly blows against Earth. Gusts of solar wind can upset the planet's electromagnetic field. Every so often the Sun spits out globs of plasma and intense bursts of radiation. These too can have a profound effect on Earth. Investigating the Sun-Earth connection is a major goal of modern space science. Robotic spacecraft are put into Earth orbit or sent out into space to collect data about this vital connection.

For decades robotic spacecraft have been designed for one-way trips. Eventually their batteries give out and their radios fail. Then they quit reporting back to Earth. They wander around in space or are incinerated by reentry into Earth's atmosphere. During the 1990s scientists developed robotic spacecraft that can do more than report back. They can come back. These sampling ships are designed to grab samples of space particles and return safely to Earth. The first one returned in September 2005. It carried samples of solar wind collected a million miles from Earth. The spaceship's name was Genesis. It marked the beginning of a whole new way for humans to explore space without even leaving the planet.