PDS_VERSION_ID = PDS3                                                         
                                                                              
LABEL_REVISION_NOTE = "                                                       
  2017-03-30  A. Raugh: Minor editing for lien resolution.                    
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  PUBLICATION_DATE   = 2017-03-30                                             
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    "A brief overview of the error bars and confidence level in the           
     derived SWAP solar wind data presented in this data set"                 
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The instrument design for the Solar Wind Around Pluto (SWAP) instrument on    
New Horizons is described by McComas et al. (2008), and the overall           
fitting procedure for the SWAP solar wind observations is described by        
Elliott et al. (2016). This document provides a very brief summary to         
provide an indication of confidence level in the data as presented.           
Interested users should consult the referenced papers for full details.       
                                                                              
The fitting procedure includes the use of a very detailed forward instrument  
response model based on laboratory energy and angular calibrations, ion       
trajectory simulations, and inflight calibration of the detector              
sensitivity and gain. Elliott et al. (2016) used a new technique developed    
by Funsten et al. (2005) to perform an inflight absolute calibration of       
the final coincidence count rates using the individual primary and            
secondary CEM (Channel Electron Multiplier) detector count rate signals.      
                                                                              
Typically, such inflight sensitivity calibrations are not performed for       
these kinds of observations; however, using this new technique Elliott et     
al. (2016) were able to perform an inflight absolute calibration of the       
coincidence rates. These final calibrated coincidence rates were used to      
derive the final solar wind density, speed and temperature values.            
                                                                              
Elliott, et al. (2016) included two figures illustrating the Poisson count    
rate error bars used in the forward model count rate model analysis of the    
fit to obtain the solar density, speed, and temperature. The error bars       
for the solar wind protons were quite small since the count rates were        
quite high. In addition, Elliott et al. (2016) demonstrated for one fit       
how much the chi-square changes when the density, speed, and temperature      
fit parameters are adjusted relative to the final fit values. The             
chi-square is well minimized in speed and steeply drops within +/-5% of       
the final fit speed value. The minimization wells for temperature and         
density are more shallow and span +/-30%. This is consistent with the         
levels of agreement typically found at 1 AU when comparing ACE and WIND       
solar wind observations. ACE and WIND speeds typically are within 5 to 10%    
of one another, and the density and temperatures are typically within 30%     
of one another. Elliott et al. (2016) also compared propagated ACE, STEREO    
A, and STEREO B solar wind speeds and those were in high agreement with       
the observed New Horizons speeds. The radial trends in the density and        
temperature were in reasonable agreement with Voyager 2 observations as       
well.                                                                         
                                                                              
References                                                                    
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Elliott, H. A., D. J. McComas, P. Valek, G. Nicolaou, S. Weidner, and         
    G. Livadiotis, 2016, The New Horizons Solar Wind Around Pluto (SWAP)      
    Observations of the Solar Wind from 11-33 AU, ApJS, 223(2), 1-21,         
    doi:10.3847/0067-0049/223/2/19.                                           
                                                                              
Funsten, H. O., Harper, R. W., & McComas, D. J., 2005, Absolute detection     
    efficiency of space-based ion mass spectrometers and neutral atom         
    imagers, Review of Scientific Instruments, 76, 3301,                      
    doi:10.1063/1.1889465.                                                    
                                                                              
McComas, D., F. Allegrini, F. Bagenal, P. Casey, P. Delamere, D.              
    Demkee, G. Dunn, H. Elliott, J. Hanley, K. Johnson, J. Langle, G.         
    Miller, S. Pope, M. Reno, B. Rodriguez, N. Schwadron, P. Valek, and S.    
    Weidner, 2008, The Solar Wind Around Pluto (SWAP) instrument aboard       
    New Horizons, Space Sci. Rev., Volume 140, Numbers 1-4, pp. 261-313,      
    doi:10.1007/s11214-007-9205-3.