Deep Space Climate Observatory

Deep Space Climate Observatory

An artist's rendering of DSCOVR satellite
Names	DSCOVR Triana GoreSat
Mission type	Space weather
Operator	NASA / NOAA
COSPAR ID	2015-007A
SATCAT no.	40390
Website	www.nesdis.noaa.gov/dscovr
Mission duration	5 years (planned) [1] 9 years, 1 month, 19 days (elapsed)
Spacecraft properties
Bus	SMEX-Lite
Manufacturer	Goddard Space Flight Center
Launch mass	570 kg (1,260 lb) [2]
Dimensions	Undeployed: 1.4 × 1.8 m (4 ft 7 in × 5 ft 11 in)
Power	600 watts
Start of mission
Launch date	11 February 2015, 23:03:42 UTC
Rocket	Falcon 9 v1.1
Launch site	Cape Canaveral, SLC-40
Contractor	SpaceX
Entered service	8 June 2015
Orbital parameters
Reference system	Heliocentric orbit[1]
Regime	Sun-Earth Lagrange point L1
Instruments PlasMag Plasma-Magnetometer NISTAR National Institute of Standards and Technology Advanced Radiometer EPIC Earth Polychromatic Imaging Camera ES Electron Spectrometer PHA Pulse Height Analyzer
DSCOVR logo Space Weather program Space Weather Follow On-Lagrange 1 →

Deep Space Climate Observatory (DSCOVR; formerly known as Triana, unofficially known as GoreSat^[3]) is a National Oceanic and Atmospheric Administration (NOAA) space weather, space climate, and Earth observation satellite. It was launched by SpaceX on a Falcon 9 v1.1 launch vehicle on 11 February 2015, from Cape Canaveral.^[4] This is NOAA's first operational deep space satellite and became its primary system of warning Earth in the event of solar magnetic storms.^[5]

DSCOVR was originally proposed as an Earth observation spacecraft positioned at the Sun-Earth L₁ Lagrange point, providing live video of the sunlit side of the planet through the Internet as well as scientific instruments to study climate change. Political changes in the United States resulted in the mission's cancellation, and in 2001 the spacecraft was placed into storage.

Proponents of the mission continued to push for its reinstatement, and a change in presidential administration in 2009 resulted in DSCOVR being taken out of storage and refurbished, and its mission was refocused to solar observation and early warning of coronal mass ejections while still providing Earth observation and climate monitoring. It launched aboard a SpaceX Falcon 9 launch vehicle on 11 February 2015, and reached L₁ on 8 June 2015, joining the list of objects orbiting at Lagrange points.

NOAA operates DSCOVR from its Satellite and Product Operations Facility in Suitland, Maryland. The acquired space data that allows for accurate weather forecasts are carried out in the Space Weather Prediction Center in Boulder, Colorado. Archival records are held by the National Centers for Environmental Information, and processing of Earth sensor data is carried out by NASA.^[1]

History

DSCOVR began as a proposal in 1998 by then-Vice President Al Gore for the purpose of whole-Earth observation at the Sun-Earth L₁ Lagrange point, 1.5×10^⁶ km (0.93×10^⁶ mi) from Earth.^[3][6] Originally known as Triana, named after Rodrigo de Triana, the first of Columbus's crew to sight land in the Americas, the spacecraft's original purpose was to provide a near-continuous view of the entire Earth and make that live image available via the Internet. Gore hoped not only to advance science with these images, but also to raise awareness of the Earth itself, updating the influential Blue Marble photograph that was taken by Apollo 17.^[7] In addition to an imaging camera, a radiometer would take the first direct measurements of how much sunlight is reflected and emitted from the whole Earth (albedo). This data could constitute a barometer for the process of global warming. The scientific goals expanded to measure the amount of solar energy reaching Earth, cloud patterns, weather systems, monitor the health of Earth's vegetation, and track the amount of UV light reaching the surface through the ozone layer.

In 1999, NASA's Inspector General reported that "the basic concept of the Triana mission was not peer reviewed", and "Triana's added science may not represent the best expenditure of NASA's limited science funding".^[8] Members of the U.S. Congress asked the National Academy of Sciences whether the project was worthwhile. The resulting report, released March 2000, stated that the mission was "strong and scientifically vital".^[9]

The Bush administration put the project on hold shortly after George W. Bush's inauguration in January 2001.^[6] Triana was removed from its original launch opportunity on STS-107 (the ill-fated Columbia mission in 2003).^[3] The US$150 million ^[3] spacecraft was placed into nitrogen blanketed storage at Goddard Space Flight Center in November 2001 and remained there for the duration of the Bush administration.^[10] NASA renamed the spacecraft Deep Space Climate Observatory (DSCOVR) in 2003 in an attempt to regain support for the project,^[3] but the mission was formally terminated by NASA in 2005.^[11]

In November 2008, funded by National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force, the spacecraft was removed from storage and underwent testing to determine its viability for launch.^[12][13] After the Obama administration took presidency in 2009, that year's budget included US$9 million marked for refurbishment and readiness of the spacecraft,^[14] resulting in NASA refurbishing the EPIC instrument and recalibrating the NISTAR instrument.^[15] Al Gore used part of his book Our Choice (2009) as an attempt to revive debate on the DSCOVR payload. The book mentions legislative efforts by senators Barbara Mikulski and Bill Nelson to get the spacecraft launched.^[16] In February 2011, the Obama administration attempted to secure funding to re-purpose the DSCOVR spacecraft as a solar observatory to replace the aging Advanced Composition Explorer (ACE) spacecraft, and requested US$47.3 million in the 2012 fiscal budget toward this purpose.^[11] Part of this funding was to allow the Naval Research Laboratory (NRL) to construct a coronal mass ejection imager for the spacecraft, but the time required would have delayed DSCOVR's launch and it was ultimately not included.^[1][11] NOAA allocated US$2 million in its 2011 budget to initiate the refurbishment effort, and increased funding to US$29.8 million in 2012.^[3]

In 2012, the Air Force allocated US$134.5 million to procure a launch vehicle and fund launch operations, both of which were awarded to SpaceX for their Falcon 9 rocket.^[3][17] In September 2013, NASA cleared DSCOVR to proceed to the implementation phase targeting an early 2015 launch,^[18] which ultimately took place on 11 February 2015.^[12] NASA's Goddard Space Flight Center is providing management and systems engineering to the mission.

In the 2017 documentary, An Inconvenient Sequel: Truth to Power, Al Gore speaks of the history of the DSCOVR spacecraft and its relation to climate change.^[19]

Spacecraft

DSCOVR is built on the SMEX-Lite spacecraft bus and has a launch mass of approximately 570 kg (1,260 lb). The main science instrument sets are the Sun-observing Plasma Magnetometer (PlasMag) and the Earth-observing NIST Advanced Radiometer (NISTAR) and Earth Polychromatic Imaging Camera (EPIC). DSCOVR has two deployable solar arrays, a propulsion module, boom, and antenna.^[20]

The propulsion module had 145 kg of N₂H₄ propellant.^[21]

From its vantage point, DSCOVR monitors variable solar wind conditions, provides early warning of approaching coronal mass ejections and observes phenomena on Earth, including changes in ozone, aerosols, dust and volcanic ash, cloud height, vegetation cover and climate. At its Sun-Earth L₁ location it has a continuous view of the Sun and of the sunlit side of the Earth. After the spacecraft arrived on-site and entered its operational phase, NASA began releasing near-real-time images of Earth through the EPIC instrument's website.^[22] DSCOVR takes full-Earth pictures about every two hours and is able to process them faster than other Earth observation satellites.^[23]

The spacecraft is in a looping halo orbit around the Sun-Earth Lagrange point L1 in a six-month period, with a spacecraft–Earth–Sun angle varying from 4° to 15°.^[24][25]

Instruments

PlasMag

The Plasma-Magnetometer (PlasMag) measures solar wind for space weather predictions. It can provide early warning detection of solar activity that could cause damage to existing satellite systems and ground infrastructure. Because solar particles reach L₁ about an hour before Earth, PlasMag can provide a warning of 15 to 60 minutes before a coronal mass ejection (CME) arrives. It does this by measuring "the magnetic field and the velocity distribution functions of the electron, proton and alpha particles (helium nuclei) of solar wind".^[26] It has three instruments:^[26]

• Magnetometer measures magnetic field
• Faraday cup measures positively charged particles
• Electrostatic analyzer measures electrons

EPIC

The Earth Polychromatic Imaging Camera (EPIC) takes images of the sunlit side of Earth for various Earth science monitoring purposes in ten different channels from ultraviolet to near-infrared. Ozone and aerosol levels are monitored along with cloud dynamics, properties of the land, and vegetation.^[29]

EPIC has an aperture diameter of 30.5 cm (12.0 in), a focal ratio of 9.38, a field of view of 0.61°, and an angular sampling resolution of 1.07 arcseconds. Earth's apparent diameter varies from 0.45° to 0.53° full width. Exposure time for each of the 10 narrowband channels (317, 325, 340, 388, 443, 552, 680, 688, 764, and 779 nm) is about 40 ms. The camera produces 2048 × 2048 pixel images, but to increase the number of downloadable images to ten per hour the resolution is averaged to 1024 × 1024 on board. The final resolution is 25 km/pixel (16 mi/pixel).^[29]

NISTAR

The National Institute of Standards and Technology Advanced Radiometer (NISTAR) was designed and built between 1999 and 2001 by NIST in Gaithersburg, MD and Ball Aerospace & Technologies in Boulder, Colorado. NISTAR measures irradiance of the sunlit face of the Earth. This means that NISTAR measures if the atmosphere of Earth is taking in more or less solar energy than it is radiating back towards space. This data is to be used to study changes in Earth's radiation budget caused by natural and human activities.^[30]

Using NISTAR data, scientists can help determine the impact that humanity is having on the atmosphere of Earth and make the necessary changes to help balance the radiation budget.^[31] The radiometer measures in four channels:

• For total radiation in ultraviolet, visible and infrared in the range 0.2–100 µm
• For reflected solar radiation in the ultraviolet, visible and near-infrared in the range 0.2–4 µm
• For reflected solar radiation in infrared in the range 0.7–4 µm
• For calibration purposes in the range 0.3–1 µm

Launch

The DSCOVR launch was conducted by launch provider SpaceX using their Falcon 9 v1.1 rocket. The launch of DSCOVR took place on 11 February 2015, following two scrubbed launches. It took DSCOVR 110 days from when it left Cape Canaveral Air Force Station (CCAFS), Florida, to reach its target destination 1.5×10^⁶ km (0.93×10^⁶ mi) away from Earth at the Sun-Earth L1 Lagrange point.^[32][33]

Launch attempt history

Operation