At first glance, it appeared to be an impressive PhotoShop image. The view of the Moon, passing in front of the sunlit face of Earth in July 2015—and revealing the fully illuminated lunar farside—looked contrived; more than a little artificial. Yet it was a true perspective of the cradle of humanity and our nearest celestial neighbor, from a distance of 930,000 miles (1.5 million km), as seen by the Deep Space Climate Observatory (DSCOVR). Launched on 11 February 2015, this joint effort between NASA, the U.S. Air Force and the National Oceanic and Atmospheric Administration (NOAA) originated in the dream of a former U.S. Vice President, but was disparagingly nicknamed a “multi-million-dollar screensaver” and delayed for years by rapidly spiraling program costs. However, today, DSCOVR marks not only a full year of operations, but represents a critical U.S. asset for Earth observation and space weather forecasting.
As outlined previously by AmericaSpace, DSCOVR rose from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., atop a SpaceX Falcon 9 v1.1 booster, becoming the Hawthorne, Calif.-based launch services provider’s first foray beyond Earth orbit. It was conceived in February 1998, by U.S. Vice President Al Gore, during his tenure under the Clinton Administration. He challenged NASA to build a relatively cheap satellite, costing between $20 million and $50 million, and weighing about 330 pounds (150 kg), for emplacement at the L1 Lagrange Point, where the gravitational influences of Earth and the Sunb meet in equilibrium. Its purpose was to broadcast real-time views of the Home Planet over the internet, every 15 minutes, via a high-definition television camera and 8-inch (20 cm) integrated telescope.
Named “Triana”, in honor Rodrigo de Triana, the Spanish lookout aboard Christopher Columbus’ ship, La Pinta—and the man who first sighted the New World on 12 October 1492—its aim was to involve university students, industry and government, as well as inspiring a new generation of scientists, explorers and engineers. NASA solicited proposals for an appropriate research payload, focused upon solar physics and climatology, and in October 1998 a pair of scientific instruments were selected. Lockheed Martin’s 10-filtered Earth Polychromatic Imaging System (EPIC) and the National Institute of Standards’ Advanced Radiometer (NISTAR) had been successfully proposed by the Scripps Institution of Oceanography at the University of California at San Diego and Dr. Francisco Valero was named as Principal Investigator. The radiometer promised to offer the first-ever direct measurements of radiant power reflected by Earth, thus contributing to humanity’s knowledge of how much solar energy is absorbed by the atmosphere, whilst EPIC would observe clouds and aerosols, as well as the Home Planet’s vegetation canopy structure and temporal evolution.
Unfortunately, Triana’s costs had already spiraled to $77 million—due in part to the inclusion of an ultraviolet-sensitive component to EPIC, as well as the addition of a Plasma Magnetometer (PLASMAG) for solar wind and magnetic field studies—and, even at this early stage, the overall payload weight had gone overbudget by 75 percent. As costs continued to increase, in September 1999 NASA Inspector-General Roberta Gross harshly criticized Triana’s scientific potential and, although a subsequent study by the National Research Council (NRC) was more sympathetic, it did not prevent the suspension of the program in early 2001. The spacecraft was placed into “Stable Suspension” storage at NASA’s Goddard Space Flight Center in Greenbelt, Md., in November 2001, pending a possible future launch opportunity.
That opportunity arose in the aftermath of the loss of Space Shuttle Columbia and, in June 2007, a “Restart Study” was concluded and NOAA later initiated a $500,000 contract with NASA to remove Triana from storage and conduct “aliveness” and other testing. By the fall of 2008—and by now renamed “DSCOVR”—it was recognized that it could be an optimal solution to many of the United States’ space weather forecasting requirements. During 2009-2011, NOAA contracted with NASA to refurbish the satellite and recalibrate its scientific instruments. Finally, in December 2012 SpaceX’s Falcon 9 was selected as the booster to deliver the 1,250-pound (570 kg) DSCOVR into space.
In its “new” guise, the mission’s primary focus would be to “continue solar wind measurements in support of space weather requirements, providing three-dimensional distribution function of the proton and alpha components of the solar wind, three-dimensional magnetic field vector and three-dimensional electron velocity distribution.” The 12-inch (30 cm) EPIC would view the entire sunlit Earth from sunrise to sunset, providing a unique angular perspective for ozone and aerosol monitoring, cloud-height measurements, planet-wide dust and volcanic ash mapping, vegetation observations and ultraviolet reflectivity. Harking back to Vice President Gore’s original idea, “a full-disk, true-color Earth image” would be produced by EPIC “about every two hours”, each publicly availably through NASA’s Langley Research Center (LaRC) in Hampton, Va., within 24 hours after their acquisition by the satellite.
Meanwhile, NISTAR would measure reflected and emitted energy in the range of 0.2-100 microns from Earth’s sunlit side, as part of ongoing efforts to investigate the impact of humanity and nature on the radiation budget. PLASMAG would yield highly accurate and rapid warnings of geomagnetic storms, with “lead times” of up to one hour. It would measurement magnetic fields and the velocity distribution functions of the electron, proton and alpha particles of the solar wind at much higher resolutions than previously attainable. Lastly, an Electron Spectrometer (ES) would provide high-temporal-resolution observations of the solar wind and a Pulse Height Analyzer (PHA) would undertake real-time measurements of particle events affecting DSCOVR’s electronics.
Launched a year ago today, DSCOVR was boosted into low-Earth orbit by the Falcon 9 v1.1, whose second stage engine performed a pair of “burns” and finally set the satellite free about 36 minutes after departing Cape Canaveral. This set it on course for a planned 110-day voyage to the L1 Lagrange Point. Within two weeks, by 24 February 2015, DSCOVR had already traveled nearly 500,000 miles (800,000 km)—halfway to L1—although it was noted that its trajectory thereafter would begin to curve somewhat.
“As DSCOVR moves further away from the Earth, the Sun’s gravity comes into play and bends the trajectory,” NOAA’s National Environmental Satellite, Data and Information Service (NESDIS) explained. “This results in curved trajectory versus a “straight-line” approach”, with an expectation that the satellite would reach L1 in early June. True to form, the announcement of its arrival on-station came on 8 June. “DSCOVR has reached its final orbit,” said Project Manager Al Vernacchio of NASA-Goddard, “and will soon be ready to begin its mission of space weather monitoring for NOAA and Earth observing for NASA.”
The satellite is expected to remain operational at L1 for about two years—joining several other missions at this Lagrangian point, including the International Sun-Earth Explorer (ISEE)-3 and the Solar and Heliospheric Observatory (SOHO)—and wasted little time in returning its first stunning imagery. On 6 July 2015, EPIC returned its first view of the entire sunlit Earth from L1. These natural-color images were generated by combining three separate monochrome exposures in rapid succession, with the red, green and blue channels of EPIC’s 10-filtered camera revealing the effect of sunlight, scattered by air molecules.
According to DSCOVR Project Scientist Adam Szabo of NASA-Goddard, the high quality of the EPIC image “exceeded all of our expectations in resolution”, whilst NASA Administrator Charlie Bolden said that the satellite demonstrated “the unique and important benefits of Earth observation from space” and enabled humanity “to see and appreciate our planet as an integrated, interacting system”.
It was stressed at the time that, once EPIC began regular data acquisition, new images of Earth would be available on a daily basis, some 12-36 hours after initially being taken, with plans to put them onto a dedicated website by September 2015. However, it seemed that DSCOVR could not wait this long. On 16 July, only a handful of days after the initial image, an astonishing view of the sunlit lunar farside passing in front of the sunlit Earth was captured by EPIC. Images were acquired between 3:50 p.m. and 8:45 p.m. EDT that day and revealed the Moon passing over the Pacific Ocean, near North America. Since our closest celestial neighbor is tidally locked to Earth—its orbital period being the same as its rotation upon its own axis—its farside is unseen by observers on Earth, but has been seen and explored by various robotic missions: firstly by the Soviet Union’s Luna-3 probe in October 1959 and more recently by the Deep Impact cometary explorer, from a distance of about 31 million miles (50 million km), on 28-29 May 2008.
As with DSCOVR’s earlier images of Earth, the views of the photobombing Moon were acquired via EPIC’s red, green and blue channels. “Combining three images, taken about 30 seconds apart as the Moon moves, produces a slight, but noticeable camera artifact on the right side of the Moon,” it was explained. “Because the Moon has moved in relation to the Earth between the time the first (red) and last (green) exposures were made, a thin green offset appears on the right side of the Moon when the three exposures are combined. This natural lunar movement also produces a slight red and blue offset on the left side of the Moon in these unaltered images.”
The perspective revealed the lunar farside’s conspicuous lack of large, dark basaltic plains, known as “maria”, compared to its Earth-facing side, and clearly revealed the large Tsiolkovsky impact crater in the southern hemisphere. That said, the farside does exhibit a handful of maria, including Mare Moscoviense—the “Sea of Moscow”—which was picked out clearly in the DSCOVR images. “It is surprising how much brighter Earth is than the Moon,” said Dr. Szabo. “Our planet is a truly brilliant object in dark space, compared to the lunar surface.”
As it presses ahead into its second year of operations, DSCOVR promises to offer many more impressive views of the Home Planet, together with its goal of a critical space-weather-forecasting sentinel. Last October, NASA launched its dedicated website for daily imagery, with the intention of revealing the entire globe over the course of a 24-hour period, with EPIC views yielding an effective resolution between 6.2 miles (10 km) and 9.4 miles (15 km). Since Earth is such a bright object, the camera is required to take very short-exposure images, ranging from 20-100 milliseconds, which removes fainter stars. On 28 October, NASA concluded its role of having launched and activated the satellite and transferred command and control over to NOAA, who will run DSCOVR for the remainder of its scientific mission. And that scientific mission, of course, encompasses far more than daily views of Earth from afar. Likened to a sensor buoy at sea, providing warning of an approaching tsunami, DSCOVR offers the capability to alert space weather forecasters of solar storms, some 15-60 minutes before they reach us.
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