How bright is the moon? Due to the moon's high appearance rate and location near our water platform, you might think this question is a good answer. If you think so, you're wrong.
We observe the Moon through the Earth's atmosphere, which causes a large error in the received lunar light, which is what we usually call spectral illumination, and it is difficult to improve the accuracy to more than 97%.
Earth's Atmosphere and Moon (Source: NASA)
But don't worry, scientists have come up with a solution to this. This method requires the use of a NASA aerial vehicle capable of flying at an altitude of 21.3 kilometers (70,000 feet). This height is just inside the stratosphere and is higher than the thickest part of the Earth's atmosphere, the troposphere. Shooting from this vantage point avoids 95% of atmospheric reflections, resulting in a sharper capture of the moon image. Researchers at the National Institute of Standards and Technology, NASA and the U.S. Geological Survey and the University of Guelph hope to use this advantage to improve measurement accuracy to 99 percent.
The mission was named the Airborne Lunar Spectral Radioluminosity Program (SPECTRAL Radiology Program) and a series of missions were conducted using ER-2 aircraft in mid-November.
ER-2 High Altitude Science Aircraft (Source: NASA)
However, scientists measure the luminosity of the moon at all times of the lunar calendar for fun (although it does sound fun).
The data collected by this program can also benefit us in other ways. Because moonlight data can help us calibrate satellites located in Earth orbit and monitor the ground. It can be a meteorological satellite, an environmental satellite, etc. used to track agriculture, drought conditions, or even seaweed activity.
In order to calibrate the element, it is necessary to use a satellite to shoot a known photometric light source, and compare the captured image with other images of the same light source taken before, if the photometric value does not match the known luminosity, the ground command station can know that the satellite's components need to be recalibrated or adjusted for sensitivity.
To achieve this, many satellites are equipped with sunlight reflectors. Sunlight is reflected through a reflector, imaged by satellites and used for calibration, do you think the two are similar?
Earth radiation balance satellite (Source: NASA)
Don't rush to build a coffin! Due to the high position and little influence of the atmosphere, strong radio radiation from the sun is rampant, causing these reflectors to wear out over time. Moonlight radiation is more stable and brighter than Earth.
So in theory, the Moon is a very ideal calibrated light source. You only need to know the relative positions of the moon and the moon that need to be calibrated to predict the moon's real-time measurement of luminosity — if you can accurately measure the energy value per unit area in the spectral irradiance or individual wavelength bandwidth.
So the team obtained complete data on the moonlight visible and near-infrared spectra in a series of missions to the ER-2 aircraft, with wavelengths ranging from 380 nanometers to 1000 nanometers. To build a high-precision moonlight model, each wavelength bandwidth measured is only a few nanometers.
The data the team has obtained is still being analyzed, but this is only a small part of the plan. Because the mission is concentrated in a few days, it can only provide a short period of lunar phase state of the moon, because a series of observation points of the moon phase, and the relative positions of the earth, the sun, and the satellite, the data obtained has a change cycle of up to 19 years.
Build reliable moonlight models for the future, which could take 3-5 years for more flights.
Prior to the implementation of the air-LUSI flight plan, the research team devised a way to describe atmospheric interference, which could effectively reduce the error caused by the interference when observing.
The team is still collecting data at the Monaroya Observatory in Hawaii. There is no doubt that the ER-2 task has effectively helped to refine the model for experiments. Monaroya Observatory will also continue to refine its database in the future – of course, more data means more accurate results.
We're one step closer than we used to be, and the luminosity of 99% accuracy is no longer far away. So, you can't run! Moon!
Lunar North Pole (Source: NASA)
Author: MICHELLE STARR
FY: Tuesday
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