Class: Ephem::SPK

Inherits:
Object
  • Object
show all
Defined in:
lib/ephem/spk.rb

Overview

The SPK class represents a SPICE Kernel (SPK) file, which contains ephemeris data for solar system bodies. It manages segments of trajectory data and provides methods to access and manipulate this data.

SPK files contain segments of ephemeris data, where each segment represents the motion of one body (target) with respect to another body (center) over a specific time period.

Examples:

Opening and using an SPK file

spk = Ephem::SPK.open("de421.bsp")
segment = spk[0, 10]
spk.close

Constant Summary collapse

TYPES = 
[
  INPOP = "IMCCE INPOP",
  JPL_DE = "JPL DE"
].freeze
INPOP_REGEXP = 
/^\s+\d{4}\.\d{5}0+$/
DE_REGEXP = 
/^[A-Z]E-(\d{4})LE-\1$/
DE_FILENAME = 
"NIO2SPK"
DATA_TYPE_IDENTIFIER = 
5

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(daf:) ⇒ SPK

Creates a new SPK instance with the given DAF.

Parameters:

  • daf (Ephem::IO::DAF) —

    The DAF (Double precision Array File) containing SPK data

Raises:

  • (ArgumentError) —

    If the DAF is nil



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# File 'lib/ephem/spk.rb', line 36

def initialize(daf:)
  raise ArgumentError, "DAF cannot be nil" if daf.nil?

  @daf = daf
  @segments = load_segments
  @pairs = build_pairs
end

Instance Attribute Details

#daf ⇒ Object (readonly)

Returns the value of attribute daf.



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# File 'lib/ephem/spk.rb', line 29

def daf
  @daf
end

#pairs ⇒ Object (readonly)

Returns the value of attribute pairs.



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# File 'lib/ephem/spk.rb', line 29

def pairs
  @pairs
end

#segments ⇒ Object (readonly)

Returns the value of attribute segments.



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# File 'lib/ephem/spk.rb', line 29

def segments
  @segments
end

Class Method Details

.open(path) ⇒ SPK

Opens an SPK file at the specified path.

Parameters:

  • path (String) —

    Path to the SPK file

Returns:

  • (SPK) —

    A new SPK instance

Raises:

  • (ArgumentError) —

    If the file cannot be accessed due to permissions



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# File 'lib/ephem/spk.rb', line 49

def self.open(path)
  daf = IO::DAF.new(File.open(path, "rb"))
  if daf.file_type == :pck
    raise ArgumentError, "#{path} is a binary PCK file, use Ephem::PCK.open"
  end

  new(daf: daf)
rescue Errno::EACCES => e
  raise ArgumentError, "File permission denied: #{path} (#{e.message})"
rescue
  daf&.close
  raise
end

Instance Method Details

#[](center, target) ⇒ Segments::Segment, Segments::PositionGroup

Retrieves the segment for a specific center-target pair.

Parameters:

  • center (Integer) —

    NAIF ID of the center body

  • target (Integer) —

    NAIF ID of the target body

Returns:

Raises:

  • (KeyError) —

    If no segment is found for the given center-target pair



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# File 'lib/ephem/spk.rb', line 90

def [](center, target)
  @pairs.fetch([center, target]) do
    raise KeyError,
      "No segment found for center: #{center}, target: #{target}"
  end
end

#close ⇒ void

This method returns an undefined value.

Closes the SPK file and cleans up resources. This method should be called when you’re done using the SPK file.



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# File 'lib/ephem/spk.rb', line 67

def close
  @daf&.close
  @segments&.each(&:clear_data)
end

#comments ⇒ String

Returns the comments stored in the SPK file.

Returns:

  • (String) —

    The comments from the DAF file



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# File 'lib/ephem/spk.rb', line 112

def comments
  @daf.comments
end

#each_segment {|segment| ... } ⇒ Enumerator, void

Iterates through all segments in the SPK file.

Yields:

  • (segment) —

    Gives each segment to the block

Yield Parameters:

Returns:

  • (Enumerator) —

    If no block is given

  • (void) —

    If a block is given



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# File 'lib/ephem/spk.rb', line 122

def each_segment(&block)
  return enum_for(:each_segment) unless block_given?

  @segments.each(&block)
end

#excerpt(output_path:, start_jd:, end_jd:, target_ids: nil, debug: false) ⇒ Object 



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# File 'lib/ephem/spk.rb', line 128

def excerpt(output_path:, start_jd:, end_jd:, target_ids: nil, debug: false)
  Excerpt
    .new(self)
    .extract(
      output_path: output_path,
      start_jd: start_jd,
      end_jd: end_jd,
      target_ids: target_ids,
      debug: debug
    )
end

#to_s ⇒ String

Returns a string representation of the SPK file.

Returns:

  • (String) —

    A description of the SPK file and its segments



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# File 'lib/ephem/spk.rb', line 75

def to_s
  <<~DESCRIPTION
    SPK file with #{@segments.size} segments:
    #{@segments.join("\n")}
  DESCRIPTION
end

#type ⇒ String?

Type of SPK file to make the difference between JPL DE and IMCCE INPOP

Returns:

  • (String, nil) —

    The type of the SPK file



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# File 'lib/ephem/spk.rb', line 100

def type
  @type ||= if @daf.record_data.internal_filename.match?(INPOP_REGEXP)
    INPOP
  elsif @daf.record_data.internal_filename == DE_FILENAME ||
      segments.first&.source&.match?(DE_REGEXP)
    JPL_DE
  end
end