As day turns to night, lights flicker on across the globe. Seen from space, the Earth becomes festooned with the tell-tale glimmers of human activity.
NASA has just released the latest satellite images of the Earth at night – the first “night light” imagery published since 2012. Produced every decade or so for the past 25 years, these global maps have been fundamental research tools, providing valuable insights into the patterns of human settlement across the planet.
However, the research team at NASA’s Earth Observing Satellite Data and Information System (EOSDIS) at the Goddard Space Flight Center in Maryland is on the verge of delivering new high-resolution images of the globe every 24 hours. The daily updates of the Earth’s night lights, to be accessible to the public soon after satellite acquisition, will help provide a clearer picture of people movement and open up the possibility of real-time applications to address pressing economic, social and environmental challenges.
The foremost challenge in capturing night-time satellite imaginary is accounting for changes in the way light is observed in different areas of the globe, whether due to the shifting phases of the moon, seasonal vegetation, clouds, aerosols, snow, ice cover or even weak atmospheric emissions such as airglow.
The researchers at EOSDIS have therefore been developing new algorithms and remote sensing techniques to detect and screen out these extraneous light sources to produce a clearer, more accurate image.
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard the Suomi NPP satellite is the first orbital instrument able to measure the intensity of the light reflections detected, thereby enabling researchers to identify the types and sources of individual night lights, such as whether they are from a street light or a fishing boat.
By automating the processing techniques and integrating the satellite data into NASA’s freely available mapping tools, Global Imagery Browse Services (GIBS) and Worldview, the team aim to make the imagery available to the public online within hours of satellite acquisition.
The researchers envisage future applications from informing recovery efforts by first responders in natural disasters, monitoring unregulated fishing activities and mapping the movement of displaced populations in war-torn countries to investigating city expansion and estimating energy usage.
Read more at NASA.