Scientists have wondered for decades just how bright the Moon is. Considering its rather close vicinity to Earth, and the fact that we’re seeing it at all times, you’d figure that would a not so complicated matter to answer. However, it is not so.
Measurements up to 99 Percent
We are seeing the Moon from Earth through the atmosphere. That generates sufficient interference that the quantity of sunlight reflected on the Moon’s surface, a calculation known as spectral irradiance, cannot be measured with over 97 percent precision.
Even if this matter seems challenging, researchers have mustered a plan. It requires the use of a high-altitude NASA plane that flies at about 21.3 kilometers (70,000 feet) – an altitude that places it in the stratosphere and above the troposphere, which is the densest layer at the base of our planet’s atmosphere.
From this particular location, 95 percent of the atmospheric interference is underneath, making it possible to snap clearer pictures of the Moon. Therefore, researchers from the National Institute of Standards and Technology (NIST), together with fellow colleagues from NASA, the United States Geological Survey (USGS), and the University of Guelph, intend to make this plan provide measurements to above 99 percent.
The project has been dubbed the Airborne Lunar Spectral Irradiance Mission, or air-LUSI managed to fly for a number of times on the ER-2 plane back in November. The scientists are not attempting to calculate the Moon’s brightness throughout all the natural satellite’s phases just for the sake of it.
This kind of data is, in fact, extremely important in other ways, due to the fact that the Moon’s brightness can be utilized to adjust satellites that are placed in Earth’s orbit and monitor the planet.
More Data is Needed
To adjust their sensors, these satellites capture an image of a source with already known brightness and collate that capture with others taken of the same source. If the new image is not the same as the one with the known brightness of the source, the tools attached to the satellite know that the sensor or the sensitivity needs to be adjusted.
A lot of satellites are carrying onboard a solar diffuser panel for this sole purpose. However, these tools deteriorate with time, due to the Sun’s powerful radiation in space.
In a set of flights aboard the ER-2 plane, the researchers calculated the trajectory of the moonlight across the whole visible and into the near-infrared spectrum. The team is still studying this data, but it is also just a small part of the complete picture.
Due to the fact that the flight has taken place across just a few days close together, it has brought just a tiny glimpse of the Moon. The Moon’s brightness varies from a specific vantage point founded on its phase, and its proportionate position to Earth and the Sun, which is on a 19-year cycle.
More data is needed; therefore, more flights will probably require a three to the five-year timeline in order to create a steady and reliable model of the Moon’s brightness over time.