Coverage for python / astro_metadata_translator / serialize / fits.py: 13%

1# This file is part of astro_metadata_translator. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (http://www.lsst.org). 

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

7# for details of code ownership. 

8# 

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

10# license that can be found in the LICENSE file. 

11 

12"""Transform ObservationInfo into "standard" FITS headers.""" 

13from __future__ import annotations 

14 

15__all__ = ("info_to_fits", "dates_to_fits", "group_to_fits") 

16 

17from typing import TYPE_CHECKING, Any, Dict, Tuple 

18 

19if TYPE_CHECKING: 

20 import astropy.time 

21 

22 from ..observationGroup import ObservationGroup 

23 from ..observationInfo import ObservationInfo 

24 

25 

26def dates_to_fits(date_begin: astropy.time.Time, date_end: astropy.time.Time) -> Dict[str, Any]: 

27 """Convert two dates into FITS form. 

28 

29 Parameters 

30 ---------- 

31 date_begin : `astropy.time.Time` 

32 Date representing the beginning of the observation. 

33 date_end : `astropy.time.Time` 

34 Date representing the end of the observation. 

35 

36 Returns 

37 ------- 

38 cards : `dict` of `str` to `str` or `float` 

39 Header card keys and values following the FITS standard. 

40 If neither date is defined this may be empty. 

41 """ 

42 cards: Dict[str, Any] = {} 

43 if date_begin is None and date_end is None: 

44 # no date headers can be written 

45 return cards 

46 

47 cards["TIMESYS"] = "TAI" 

48 

49 date_avg = None 

50 if date_begin is not None and date_end is not None: 

51 date_avg = date_begin + (date_end - date_begin) / 2.0 

52 

53 for fragment, date in (("OBS", date_begin), ("END", date_end), ("AVG", date_avg)): 

54 if date is not None: 

55 tai = date.tai 

56 cards[f"DATE-{fragment}"] = tai.isot 

57 cards[f"MJD-{fragment}"] = tai.mjd 

58 

59 return cards 

60 

61 

62def info_to_fits(obs_info: ObservationInfo) -> Tuple[Dict[str, Any], Dict[str, str]]: 

63 """Convert an `ObservationInfo` to something suitable for writing 

64 to a FITS file. 

65 

66 Parameters 

67 ---------- 

68 obs_info : `ObservationInfo` 

69 Standardized observation information to transform to FITS headers. 

70 

71 Returns 

72 ------- 

73 cards : `dict` of `str` to (`int`, `float`, `str`, `bool`) 

74 FITS header keys and values in form understood by FITS. 

75 comments : `dict` of `str` to `str` 

76 Suitable comment string. There will be at most one entry for each key 

77 in ``cards``. 

78 """ 

79 

80 cards = {} 

81 comments = {} 

82 

83 if obs_info.instrument is not None: 

84 cards["INSTRUME"] = obs_info.instrument 

85 comments["INSTRUME"] = "Name of instrument" 

86 

87 cards.update(dates_to_fits(obs_info.datetime_begin, obs_info.datetime_end)) 

88 

89 return cards, comments 

90 

91 

92def group_to_fits(obs_group: ObservationGroup) -> Tuple[Dict[str, Any], Dict[str, str]]: 

93 """Convert an `ObservationGroup` to something suitable for writing 

94 to a FITS file. 

95 

96 Parameters 

97 ---------- 

98 obs_group : `ObservationGroup` 

99 Collection of observation information to transform to a single 

100 FITS header. 

101 

102 Returns 

103 ------- 

104 cards : `dict` of `str` to (`int`, `float`, `str`, `bool`) 

105 FITS header keys and values in form understood by FITS. 

106 comments : `dict` of `str` to `str` 

107 Suitable comment string. There will be at most one entry for each key 

108 in ``cards``. 

109 """ 

110 

111 cards = {} 

112 comments = {} 

113 

114 oldest, newest = obs_group.extremes() 

115 

116 instruments = obs_group.property_values("instrument") 

117 if len(instruments) == 1: 

118 cards["INSTRUME"] = list(instruments)[0] 

119 comments["INSTRUME"] = "Name of instrument" 

120 

121 cards.update(dates_to_fits(oldest.datetime_begin, newest.datetime_end)) 

122 

123 return cards, comments