Doug Bonderud

Nov 6th 2020

Pics or It Didn’t Happen: The History-Making Snap of Explorer 6


Let’s be honest: It’s not a great photo — taken by Explorer 6, the first satellite image of Earth was a blocky, blurry mess. But it was also a history-making achievement that helped fuel human imagination and kick off decades of outer space discovery.

Not Exactly Earth’s Best Look

On Aug. 14, 1959, the sixth Explorer iteration captured the first satellite image of Earth. Snapped above a partly cloudy stretch of the central Pacific Ocean, it took 40 minutes for picture data to make the trip from the Explorer 6 to a receiving station in Hawaii. Compared to current photo-taking technology, the Explorer’s black-and-white image is crude at best and bears little resemblance to later, higher-resolution photos taken both from orbit and the lunar surface.

Considering the conditions of capture, however, the photograph was a stunning achievement. Not only was the spacecraft more than 16,700 feet above Earth’s surface and moving more than 20,000 miles per hour, it was also operating with just 63% power since only three of its solar cells were operating. Nonetheless, Explorer lived up to its namesake by giving humankind the first glimpse of Earth from orbit.

The Science of Solar Snaps

NASA’s Explorer series of satellites came with a clear mission: “To provide frequent flight opportunities for scientific investigations from space.” Achieving this goal meant designing and deploying spacecraft that were lightweight, relatively low-cost and focused on specific scientific observations.

Launched under U.S. Army auspices on Jan. 31, 1958, Explorer 1 ushered in a new era of space exploration. Control of the program was then transferred to NASA when the space agency opened its doors in October 1958 — and on Aug. 7, 1959, Explorer 6 blasted off into space.

Often known as “paddlewheel” satellites thanks to the shape and positioning of their four solar panels, Explorer-type craft were purpose-built for mission mandates, allowing NASA to substantially increase the pace of solar scientific discoveries. In the first decade of this program alone, the agency launched 35 Explorers to help expand the scope of human understanding.

Version 6 followed the typical production pattern: According to NASA, It was a small, spheroid-shaped satellite “designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the upper atmosphere, and the flux of micrometeorites.” It also carried a scanning device designed for capturing pictures of Earth’s cloud cover. Coming in at just over 142 pounds, the satellite was launched into a highly elliptical orbit. NASA engineers stabilized the craft’s spin at 2.8 revolutions per second (rps) with a right ascension spin axis of 217 degrees and a declination of 23 degrees. Unfortunately, only three of the four solar panels fully extended, leaving Explorer 6 with just 63% power. This caused significant signal noise and gave NASA limited operational time before the craft went dark.

Oct. 6, 1959 marked the last spacecraft contact as power failed — but despite having less than two months operational time under its orbital belt, Explorer 6 managed to record 827 hours of analog data, 23 hours of digital data and make history with the first satellite image of Earth.

Fueling the Future of Extra-Earth Exploration

Along with snapping Earth’s photo from a distance, Explorer 6 also conducted the first in-depth survey of the Van Allen radiation belt. However, this wouldn’t have been possible without previous Explorer missions; Explorer 1 detected this radiation saturation 600 miles above Earth, prompting astrophysicist James Van Allen to posit the existence of trapped solar particles.

Subsequent Explorer missions helped solve more solar mysteries by confirming the presence of helium in the upper atmosphere, determining that the interplanetary magnetic field is primarily powered by the sun’s magnetic field and demonstrating the existence of solar wind shock waves on Earth’s magnetosphere.

The Explorer series also laid the groundwork for NASA’s famous Apollo initiative. Not only were solar solutions and scientific instruments critical to help inform Apollo craft design, but the potential for cameras to capture Earth from space led to rapid advancement in picture-taking technologies. It’s not a stretch to say that without the legacy and legwork of Explorer craft, Apollo 8’s famous “Earthrise” image might not exist.

Teamwork Makes the Dream Work

Put simply? Taking on the task of space exploration at scale is a team effort. From the “failed” Pioneer 4 craft to Explorer, Voyager, Gemini and Apollo missions, each investigative iteration builds on its predecessors to fly further, dig deeper and expand the scope of space exploration.

Sure, the first satellite snap of Earth wasn’t great, but it proved the point: Seeing is believing — and drives scientific achieving.