rnsf

Define and load a phase function data format
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rnsf.5 (4457B)


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      8 .\" Copyright (C) 2022, 2023 Université Paul Sabatier
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     22 .Dd September 15, 2023
     23 .Dt RNSF 5
     24 .Os
     25 .Sh NAME
     26 .Nm rnsf
     27 .Nd Rad-Net Scattering Functions file format
     28 .Sh DESCRIPTION
     29 .Nm
     30 is a text file format that describes a phase function whose type and parameters
     31 can vary spectrally.
     32 Its data are described for a set of wavelengths or spectral bands that must be
     33 listed in ascending order.
     34 .Pp
     35 Characters behind the hash mark
     36 .Pq Li #
     37 are considered comments and are therefore ignored, as well as empty lines,
     38 i.e. lines without any characters or composed only of spaces and tabs.
     39 .Pp
     40 The file format is as follows:
     41 .Bl -column (per-band-phase-func) (::=) ()
     42 .It Ao Va rnsf Ac Ta ::= Ta Ao Va per-wlen-phase-func Ac |
     43 .Ao Va per-band-phase-func Ac
     44 .It \  Ta Ta
     45 .It Ao  Va per-wlen-phase-func Ac Ta ::= Ta
     46 .Li wavelengths
     47 .Aq Va wavelengths-count
     48 .It Ta Ta Aq Va wlen-phase-func
     49 .It Ta Ta Va ...
     50 .It Ao Va wlen-phase-func Ac Ta ::= Ta Ao Va wavelength Ac Ao Va phase-func Ac
     51 .It Ao Va wavelengths-count Ac Ta ::= Ta Va integer
     52 .It Ao Va wavelength Ac Ta ::= Ta Va real
     53 # In nanometers
     54 .It \  Ta Ta
     55 .It Ao Va per-band-phase-func Ac Ta ::= Ta
     56 .Li bands
     57 .Aq Va bands-count
     58 .It Ta Ta Aq Va band-phase-func
     59 .It Ta Ta Va ...
     60 .It Ao Va band-phase-func Ac Ta ::= Ta
     61 .Aq Va length-min
     62 .Aq Va length-max
     63 .Aq Va phase-func
     64 .It Ao Va bands-count Ac Ta ::= Ta Va integer
     65 .It Ao Va length-min Ac Ta ::= Ta Va real
     66 # Inclusive bound in nanometers
     67 .It Ao Va length-max Ac Ta ::= Ta Va real
     68 # Inclusive bound in nanometers
     69 .It \  Ta Ta
     70 .It Ao Va phase-func Ac Ta ::= Ta Ao Va phase-func-HG Ac |
     71 .Ao Va phase-func-discrete Ac
     72 .It \  Ta Ta
     73 .It Ao Va phase-func-HG Ac Ta ::= Ta Li HG Aq Va asymmetric-param
     74 .It Ao Va asymmetric-param Ac Ta ::= Ta Va real
     75 # In
     76 .Bq -1, 1
     77 .It \  Ta Ta
     78 .It Ao Va phase-func-discrete Ac Ta ::= Ta Li discrete Aq Va angles-count
     79 .It Ta Ta Li 0 Aq Va value
     80 .It Ta Ta Op Ao Va pair Ac Va ...
     81 # Ascending angles
     82 .It Ta Ta Li 3.14159 Aq Va value
     83 .It Ao Va angles-count Ac Ta ::= Ta Va integer
     84 # Must be >= 2
     85 .It Ao Va pair Ac Ta ::= Ta Ao Va theta Ac Ao Va value Ac
     86 .It Ao Va theta Ac Ta ::= Ta Va real
     87 # In radians
     88 .It Ao Va value Ac Ta ::= Ta Va real
     89 # Not necessarily normalized
     90 .El
     91 .Sh EXAMPLES
     92 Spectrally varying phase function on two spectral bands: a band for the visible
     93 part of the spectrum for which a Henyey & Greenstein phase function is used,
     94 and a band for long waves with a discretized phase function on 4 angles:
     95 .Bd -literal -offset Ds
     96 bands 2
     97 
     98 # Visible part
     99 380 780 HG 0
    100 
    101 # Inrared
    102 1000 100000 discrete 4
    103   0       0.079577
    104   0.78    0.079577
    105   2.35    0.079577
    106   3.14159 0.079577
    107 .Ed
    108 .Pp
    109 Phase function for a set of 10 wavelengths.
    110 Use a discrete phase function for short waves and Henyey & Greenstein for long
    111 waves:
    112 .Bd -literal -offset Ds
    113 wavelengths 10
    114 
    115 # Short waves
    116 430 discrete 8
    117   0           0.02
    118   0.23        0.04
    119   0.5         0.07
    120   0.7         0.15
    121   1.54        1.23
    122   1.8         0.02
    123   2           1.23
    124   3.14159     0.79
    125 450 discrete 2
    126   0           0.5
    127   3.14159     0.796
    128 750 discrete 4
    129   0           0.079577
    130   0.78        0.079577
    131   2.35        0.079577
    132   3.14159     0.079577
    133 
    134 # Long waves
    135 1100    HG   -0.1
    136 1300    HG    0.57
    137 1400    HG    0.4
    138 2100    HG    0.3
    139 2500    HG   -0.9
    140 2900    HG   -0.4
    141 100000  HG    0.0
    142 .Ed
    143 .Sh HISTORY
    144 The
    145 .Nm
    146 format was first developed for the
    147 .Xr htrdr-planeto 1
    148 program.