After an international team worked for six days and nights dredging sand to free a giant container ship blocking the Suez Canal, the high spring tide from a super moon finally helped set the Ever Given free. The quarter-mile-long ship, which had become wedged in muck and clay along the banks of the canal, was “refloated” at about 3 pm local time Monday, and tugboat horns blared in celebration.
In the early hours of March 29, Day Night Band imagery from the NOAA-20 satellite was able to capture images of the more than 400 ships backed up on both sides of the operation, in the Red Sea and Bitter Lake. And 100 percent illumination from the moon allowed for clear images of the land and water features. Because of the high spring tide, which occurs when the Earth, Sun and Moon are in alignment, water rose about 18 inches above normal levels.
The Day-Night Band is part of the Suomi-NPP and NOAA-20 satellites’ VIIRS instrument. In the dark, the human eye dilates to allow in more light, and this improves night vision. Similarly, the Day-Night Band instrument sees a broad spectrum of light ranging in wavelengths from green at 500 nanometers to near infrared at 900 nanometers. Due to the wide spectrum, the sensor is highly sensitive to light. With filtering techniques, the Day-Night Band can also distinguish between city lights, moonlight, auroras and other light sources, such as light from ships.