NREL's Solar and Moon Position Algorithm (SAMPA)
This algorithm calculates the solar and lunar zenith and azimuth angles in the period from the year -2000 to 6000, with uncertainties of +/- 0.0003 degrees for the Sun and +/- 0.003 degrees for the Moon, based on the date, time, and location on Earth. The algorithm can be used for solar eclipse monitoring and estimating the reduction in solar irradiance for many applications, such as smart grid, solar energy, etc. The software has not been tested on a variety of platforms and is not guaranteed to work on yours. It is provided here as a convenience.
This algorithm is available in ANSI C; how to use this algorithm and a description of the variables is included in the
sampa.h header file. Further information on this algorithm is available in the following
NREL technical report:
Reda, I. (2010). Solar Eclipse Monitoring for Solar Energy Applications Using the Solar and Moon Position Algorithms. 35 pp.; NREL Report No. TP-3B0-47681. (927 KB PDF Document)
SAMPA.CDistributed by the National Renewable Energy Laboratory
Solar Radiation Research Laboratory
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|The software is being provided for internal, noncommercial purposes only and shall not be re-distributed. Please contact Jean Schulte in the NREL Commercialization and Technology Transfer Office for information concerning a commercial license to use the software.|
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SAMPA for ANSI C:
- sampa.c -- C modular code that computes the lunar position in the sky and eclipse conditions, revised September 8, 2014.
- sampa.h -- the header file that must be included in the code that calls "sampa.c"
- spa.c -- NREL's Solar Position Algorithm (SPA) source code that is called by "sampa.c"
- spa.h -- NREL's Solar Position Algorithm (SPA) header file that is included in "sampa.c"
- bird.c -- SERI/NREL Clear Sky Broadband Solar Radiation Model source code, required if the user is interested in modeled irradiance during an eclipse, revised May 11, 2017.
- bird.h -- the header file that is included in "sampa.c"
- sampa_tester.c -- a test code, containing the main() function, that exercises "sampa.c"
Note: An online SAMPA calculator that uses this source code is also available.