Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

# This file is part of astro_metadata_translator. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (http://www.lsst.org). 

# See the LICENSE file at the top-level directory of this distribution 

# for details of code ownership. 

# 

# Use of this source code is governed by a 3-clause BSD-style 

# license that can be found in the LICENSE file. 

 

"""Generically useful translation helpers which translation classes 

can use. 

 

They are written as free functions. Some of them are written 

as if they are methods of `MetadataTranslator`, allowing them to be attached 

to translator classes that need them. These methods have full access to 

the translator methods. 

 

Other functions are pure helpers that can be imported and used to help 

translation classes without using `MetadataTranslator` properties. 

 

""" 

 

__all__ = ("to_location_via_telescope_name", 

"is_non_science", 

"tracking_from_degree_headers", 

"altitude_from_zenith_distance") 

 

import logging 

from astropy.coordinates import EarthLocation, SkyCoord, AltAz 

import astropy.units as u 

 

log = logging.getLogger(__name__) 

 

 

def to_location_via_telescope_name(self): 

"""Calculate the observatory location via the telescope name. 

 

Returns 

------- 

loc : `astropy.coordinates.EarthLocation` 

Location of the observatory. 

""" 

return EarthLocation.of_site(self.to_telescope()) 

 

 

def is_non_science(self): 

"""Raise an exception if this is a science observation. 

 

Raises 

------ 

KeyError 

Is a science observation. 

""" 

if self.to_observation_type() == "science": 

raise KeyError("Header represents science observation and can not default") 

return 

 

 

def altitude_from_zenith_distance(zd): 

"""Convert zenith distance to altitude 

 

Parameters 

---------- 

zd : `astropy.units.Quantity` 

Zenith distance as an angle. 

 

Returns 

------- 

alt : `astropy.units.Quantity` 

Altitude. 

""" 

return 90.*u.deg - zd 

 

 

def tracking_from_degree_headers(self, radecsys, radecpairs, unit=u.deg): 

"""Calculate the tracking coordinates from lists of headers. 

 

Parameters 

---------- 

radecsys : `list` or `tuple` 

Header keywords to try corresponding to the tracking system. If none 

match ICRS will be assumed. 

radecpairs : `tuple` of `tuple` of pairs of `str` 

Pairs of keywords specifying the RA/Dec in units of ``unit``. 

unit : `astropy.unit.BaseUnit` or `tuple` 

Unit definition suitable for the `~astropy.coordinate.SkyCoord` 

constructor. 

 

Returns 

------- 

radec = `astropy.coordinates.SkyCoord` 

The RA/Dec coordinates. None if this is a moving target or a 

non-science observation without any RA/Dec definition. 

 

Raises 

------ 

KeyError 

No RA/Dec keywords were found and this observation is a science 

observation. 

""" 

used = [] 

for k in radecsys: 

if self.is_key_ok(k): 

frame = self._header[k].strip().lower() 

used.append(k) 

if frame == "gappt": 

self._used_these_cards(*used) 

# Moving target 

return None 

break 

else: 

frame = "icrs" 

for ra_key, dec_key in radecpairs: 

if self.are_keys_ok([ra_key, dec_key]): 

radec = SkyCoord(self._header[ra_key], self._header[dec_key], 

frame=frame, unit=unit, obstime=self.to_datetime_begin(), 

location=self.to_location()) 

self._used_these_cards(ra_key, dec_key, *used) 

return radec 

if self.to_observation_type() == "science": 

raise KeyError("Unable to determine tracking RA/Dec of science observation") 

return None 

 

 

def altaz_from_degree_headers(self, altazpairs, obstime, is_zd=None): 

"""Calculate the altitude/azimuth coordinates from lists of headers. 

 

If the altitude is found but is greater than 90 deg, it will be returned 

fixed at 90 deg. 

If the altitude or azimuth are negative and this is a calibration 

observation, `None` will be returned. 

 

Parameters 

---------- 

altazpairs : `tuple` of `str` 

Pairs of keywords specifying Alt/Az in degrees. Each pair is tried 

in turn. 

obstime : `astropy.time.Time` 

Reference time to use for these coordinates. 

is_zd : `set`, optional 

Contains keywords that correspond to zenith distances rather than 

altitude. 

 

Returns 

------- 

altaz = `astropy.coordinates.AltAz` 

The AltAz coordinates associated with the telescope location 

and provided time. Returns `None` if this observation is not 

a science observation and no AltAz keys were located. 

 

Raises 

------ 

KeyError 

No AltAz keywords were found and this observation is a science 

observation. 

""" 

for alt_key, az_key in altazpairs: 

if self.are_keys_ok([az_key, alt_key]): 

az = self._header[az_key] 

alt = self._header[alt_key] 

 

# Check for zenith distance 

if is_zd and alt_key in is_zd: 

alt = altitude_from_zenith_distance(alt * u.deg).value 

 

if az < -360.0 or alt < 0.0: 

# Break out of loop since we have found values but 

# they are bad. 

break 

if alt > 90.0: 

log.warning("Clipping altitude (%f) at 90 degrees", alt) 

alt = 90.0 

 

altaz = AltAz(az * u.deg, alt * u.deg, 

obstime=obstime, location=self.to_location()) 

self._used_these_cards(az_key, alt_key) 

return altaz 

if self.to_observation_type() == "science": 

raise KeyError("Unable to determine AltAz of science observation") 

return None