In the 50 years since satellites first went into orbit, the readings they've provided have given science a huge boost.
Now scientists are trying to give a boost to a new generation of satellites that will monitor the changes sweeping over our planet.
Over the past week, much of the world's attention has been focused on a U.S. spy satellite that is falling from orbit and may be brought down within days. But here in Boston, at the annual meeting of the American Association for the Advancement of Science, researchers focused on spacecraft that are still on the job, sending back data for peaceful purposes rather than military advantage.
"The cost of Earth observations from space might have been measured in the billions," said Colby College professor James Fleming, who focuses on the impact of science and technology on society. "But the value of knowing your home planet is priceless."
This weekend's scientific sessions followed up on a retrospective on Earth observations commissioned by the National Research Council. America's stream of orbital observations began 50 years ago with the launch of the Explorer 1 satellite. The data from Explorer 1 and follow-up satellites revealed that Earth was surrounded by belts of radiation — a hazard that was taken into account for the unmanned and manned space missions that followed.
"We made a fantastic discovery on our first try," Fleming said.
More discoveries followed, to such an extent that Fleming said it would be hard to imagine how modern society could function without Earth-watching spacecraft. "We've become, in that sense, more interdependent," he said.
Among the milestones:
- Weather monitoring: Meteorology was among the first applications for satellite technology, ranked alongside telecommunications and military surveillance. Since 1960, thousands of lives have been saved through hurricane forecasting alone. The first in a new generation of weather satellites was launched in 2006, and the technology for analyzing satellite data continues to improve. "Global seven-day forecasts are as good as Northern Hemisphere five-day forecasts were 25 years ago," said Stan Kidder, senior research scientist at Colorado State University's Cooperative Institute for Research in the Atmosphere.
- The Overview Effect: Pictures of Earth taken during the Apollo missions in the 1960s and early ’70s gave a powerful push to the environmental movement, as well as a sense of planetary kinship that has been termed the "Overview Effect." Fleming noted that "the 'Blue Marble' image is an icon." Updated imagery of the home planet — including a next-generation Blue Marble based on contemporary satellite imagery — has a similar effect today.
- Ozone monitoring: Satellites have been tracking threats to the ozone layer, which protects Earth from harmful ultraviolet radiation since the 1970s. In 1987, the findings beamed back from space helped lead to the Montreal Protocol, a treaty that limits the production of ozone-destroying industrial chemicals. Thanks to the treaty, scientists expect the ozone layer to make a complete recovery by 2071, said John Gille, a scientist at the National Center for Atmospheric Research at the University of Colorado. "This is the best environmental story we have to date," he said.
- Environmental monitoring: Today, legions of satellites are documenting the effects of pollution and global climate change on the planet's land and oceans, its atmosphere and ice sheets. To cite just one example, satellite readings have shown that the oceans' phytoplankton were responsible for almost half of the planet's primary biomass production. Janet Campbell, director of the University of New Hampshire's Ocean Process Analysis Laboratory called that discovery "one of the most incredible achievements" in the effort to understand Earth's carbon cycle.
As satellites send back more data about the interactions involving Earth's atmosphere, oceans and land, scientists are getting a better fix on how biology and climate work together. "The next frontier is the coastal oceans," Campbell said.
The data also may suggest better fixes for what many see as a climate crisis. Based on readings from satellite-borne sensors, some scientists have tried seeding areas of the planet's southern oceans with iron to encourage plankton growth and lock up more carbon from the atmosphere.
Worrying about the future
However, the spacecraft carrying those sensors are beyond or nearly beyond their design lifetimes — and the satellites that were intended to replace them have not yet been launched, due to technical and budgetary problems. "Unfortunately, the plans that the U.S. has for these missions are now at jeopardy of being lost," Campbell said.
Scientists first sounded the alarm about the potential satellite gap a year ago. Since then, the White House has been trying to come up with less expensive options, while NASA included more money for Earth-observing satellites in this month's budget proposal.
Nevertheless, Campbell and others worry that it may be a case of too little, too late.
"There's likely to be a gap, first of all, and secondly the quality is not going to be as high-resolution," Campbell said.
U.S. scientists may have to rely on the European Space Agency's satellites to fill that gap — even though the data may sometimes be difficult to mesh together.
"Maybe we will be able to thank our European friends for continuing the record," Campbell said.