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Ephemeris readers (#732)
* Add NISAR orbit and attitude product readers. * Add docstring, type annotations, and epoch option. * Add orbit reader test case. * Improve attitude docs, change assert to exception * Add attitude reader test * Fix typo * Give better error for malformed orbit data. * Eliminate blank lines between parameters in docs. * Clarify default band in docs * Prefer generator to list. * Start compendium of test data origin stories. * Make attitude more robust to bad input data.
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‎python/packages/pybind_nisar/products/readers/__init__.py‎

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from .SLC import SLC
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from . import Raw
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from . import antenna
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from .attitude import load_attitude_from_xml
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from .orbit import load_orbit_from_xml
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# end of file

‎python/packages/pybind_nisar/products/readers/attitude.py‎

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import xml.etree.ElementTree as ET
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from isce3.core import DateTime, Quaternion, Attitude
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def _require(node: ET.Element, pattern: str) -> ET.Element:
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"""Like Element.find but error if no match is found.
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"""
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x = node.find(pattern)
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if x is None:
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raise IOError(f"Could not find XML element '{pattern}'")
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return x
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def load_attitude_from_xml(f, epoch: DateTime = None, band="L") -> Attitude:
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"""Load attitude from XML file.
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Parameters
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----------
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f : str, Path, or file
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File name or object containing XML data.
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epoch : isce3.core.DateTime, optional
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Desired reference epoch, defaults to time of first state vector.
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band : {'L', 'S'}, optional
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Which frequency band to read, default to 'L'.
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Returns
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-------
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attitude : isce3.core.Attitude
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Attitude object.
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Notes
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-----
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File format is described in NISAR Radar Pointing Product SIS, JPL D-102264.
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It contains information that may not be parsed or represented in the
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output object.
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"""
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if band not in ("L", "S"):
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raise ValueError(f"Expected band in {{'L', 'S'}} got {band}")
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root = ET.parse(f).getroot() # radarPointing
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svl = _require(root, f"{band}SAR/radarPointingStateVectorList")
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n = int(svl.attrib["count"])
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if n <= 0:
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raise ValueError(f"Need multiple quaternions, got count={n}")
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datetimes, qs = [], []
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for node in svl.findall("radarPointingStateVector"):
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t = DateTime(_require(node, "utc").text)
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q = (float(_require(node, name).text)
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for name in ("q0", "q1", "q2", "q3"))
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datetimes.append(t)
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qs.append(Quaternion(*q))
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if len(datetimes) != n:
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raise IOError(f"Expected {n} attitude entries, got {len(datetimes)}")
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if epoch is None:
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epoch = datetimes[0]
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# NOTE Assume times are sorted and let Attitude ctor throw error if not.
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times = [(t - epoch).total_seconds() for t in datetimes]
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return Attitude(times, qs, epoch)

‎python/packages/pybind_nisar/products/readers/orbit.py‎

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import xml.etree.ElementTree as ET
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from isce3.core import DateTime, StateVector, Orbit
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def load_orbit_from_xml(f, epoch: DateTime = None) -> Orbit:
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"""Load orbit from XML file.
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Parameters
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----------
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f : str, Path, or file
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File name or object containing XML data.
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epoch : isce3.core.DateTime, optional
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Desired reference epoch, defaults to time of first state vector.
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Returns
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-------
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orbit : isce3.core.Orbit
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Orbit object
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Notes
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-----
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File format is described in NISAR Orbit Ephemeris Product SIS, JPL D-102253.
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It contains information such as covariance estimates and maneuvers that
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are not parsed or represented in the output object.
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"""
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root = ET.parse(f).getroot()
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svl = root.find("orbitStateVectorList")
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if svl is None:
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raise IOError("Could not parse orbit XML file.")
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n = int(svl.attrib["count"])
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states = []
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for node in svl.findall("orbitStateVector"):
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t = DateTime(node.find("utc").text)
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x = [float(node.find(name).text) for name in "xyz"]
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v = [float(node.find(name).text) for name in ("vx", "vy", "vz")]
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states.append(StateVector(t, x, v))
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if len(states) != n:
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raise IOError(f"Expected {n} orbit state vectors, got {len(states)}")
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if epoch is None:
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epoch = states[0].datetime
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return Orbit(states, epoch)

‎tests/data/README.md‎

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# Test Data
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This README gives brief descriptions on the generation of various test data
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found in this directory.
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## Winnipeg
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- The original product from which the test data are generated: winnip_31604_12061_004_120717_L090_CX_129_05.h5
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This is a UAVSAR NISAR simulated product. Check science/LSAR/identification/productVersion to get the product version
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As for NISAR data/ Simulated NISAR data have to be intended as zero-doppler
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- All winnipeg-related "reference" products in this folder (e.g. warped_winnipeg.slc) have been generated using ISCE2 v2.3.
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The ISCE2 processing uses "winnip_31604_12061_004_120717_L090_CX_129_05.h5" as reference and secondary SLC to create the golden/reference dataset.
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## Attitude
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Attitude sample data in NISAR format (see JPL D-102264) was provided by the
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G&C team (Dave Bates, et al) during NASA Internal Thread Test 04 (NITT-04)
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activities in late 2020/early 2021. The hash of the original file delivered
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by email is
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```
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$ md5sum NISAR_ANC_L_PR_FRP_20210114T023357_20200107T200000_20200109T040000.xml
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2101bddf088d3b4e8e0e3051931f8284 NISAR_ANC_L_PR_FRP_20210114T023357_20200107T200000_20200109T040000.xml
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```
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To reduce the size of the test data, this file was trimmed to the first ten
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records to produce `attitude.xml`.
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## Orbit
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Orbit sample data in NISAR format (see JPL D-102253) provided by Paul Ries
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via email on 2020-07-06. It was generated from Jason2 data. The hash of the
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original file is
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```
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$ md5sum -b smoothFinal.xml.gz
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f415fc38e1feff0bb1453782be3d2b5f *smoothFinal.xml.gz
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```
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This file was uncompressed and trimmed to the first ten state vectors in
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order to reduce the size of the `orbit.xml` file stored here.

‎tests/data/attitude.xml‎

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<?xml version='1.0' encoding='utf-8'?>
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<radarPointing>
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<productInformation>
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<productName>NISAR_ANC_L_PR_FRP_20210114T023357_20200107T200000_20200109T040000</productName>
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<mission>NISAR</mission>
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<validityStartDateTime>2020-01-07T20:00:00</validityStartDateTime>
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<validityEndDateTime>2020-01-09T04:00:00</validityEndDateTime>
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<fileClass>Test</fileClass>
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<fileType>FRP</fileType>
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<creator>NASA JPL</creator>
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<creationDateTime>2021-01-14T02:33:57.547520</creationDateTime>
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</productInformation>
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<LSAR>
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<radarPointingStateVectorList count="10">
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<radarPointingStateVector index="1">
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<utc>2020-01-07T20:00:00</utc>
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<roll>-0.6457081417495419</roll>
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<pitch>0.001398760112229801</pitch>
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<yaw>1.5697422973092137</yaw>
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<q0>0.45998636868613685</q0>
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<q1>0.8484777808560364</q1>
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<q2>0.2604469244480131</q2>
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<q3>-0.02579526239696106</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="2">
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<utc>2020-01-07T20:00:01</utc>
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<roll>-0.6457082357320937</roll>
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<pitch>0.0013966873285031834</pitch>
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<yaw>1.56974385895192</yaw>
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<q0>0.46031535338895463</q0>
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<q1>0.8483862072201784</q1>
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<q2>0.26013727118041524</q2>
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<q3>-0.026061829862272068</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="3">
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<utc>2020-01-07T20:00:02</utc>
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<roll>-0.6457083225750708</roll>
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<pitch>0.0013946167258813244</pitch>
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<yaw>1.5697454189676887</yaw>
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<q0>0.46064424123610703</q0>
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<q1>0.848294362825532</q1>
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<q2>0.2598275841825737</q2>
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<q3>-0.026328378459064716</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="4">
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<utc>2020-01-07T20:00:03</utc>
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<roll>-0.6457084155535049</roll>
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<pitch>0.001392541161273757</pitch>
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<yaw>1.5697469827093893</yaw>
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<q0>0.46097303216847363</q0>
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<q1>0.8482022476809679</q1>
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<q2>0.25951786356037376</q2>
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<q3>-0.026594908073106494</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="5">
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<utc>2020-01-07T20:00:04</utc>
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<roll>-0.6457084957779009</roll>
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<pitch>0.0013904611131749993</pitch>
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<yaw>1.569748549857765</yaw>
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<q0>0.46130172612701786</q0>
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<q1>0.8481098617954342</q1>
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<q2>0.2592081094196022</q2>
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<q3>-0.026861418590215513</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="6">
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<utc>2020-01-07T20:00:05</utc>
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<roll>-0.6457085924112703</roll>
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<pitch>0.0013883550254227123</pitch>
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<yaw>1.5697501365908249</yaw>
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<q0>0.4616303230527267</q0>
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<q1>0.8480172051779915</q1>
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<q2>0.25889832186595574</q2>
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<q3>-0.027127909896180857</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="7">
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<utc>2020-01-07T20:00:06</utc>
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<roll>-0.6457086856447454</roll>
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<pitch>0.0013862513498051777</pitch>
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<yaw>1.5697517215146415</yaw>
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<q0>0.46195882288646645</q0>
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<q1>0.847924277837868</q1>
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<q2>0.25858850100511505</q2>
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<q3>-0.02739438187672999</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="8">
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<utc>2020-01-07T20:00:07</utc>
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<roll>-0.6457087747620623</roll>
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<pitch>0.0013841327533615703</pitch>
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<yaw>1.5697533176903113</yaw>
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<q0>0.46228722556915264</q0>
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<q1>0.847831079784391</q1>
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<q2>0.25827864694266167</q2>
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<q3>-0.027660834417580382</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="9">
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<utc>2020-01-07T20:00:08</utc>
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<roll>-0.6457088614413605</roll>
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<pitch>0.0013820105542763858</pitch>
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<yaw>1.569754916586475</yaw>
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<q0>0.4626155310417434</q0>
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<q1>0.8477376110269874</q1>
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<q2>0.25796875978409056</q2>
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<q3>-0.027927267404464606</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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<radarPointingStateVector index="10">
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<utc>2020-01-07T20:00:09</utc>
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<roll>-0.6457089578199849</roll>
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<pitch>0.0013798794032847958</pitch>
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<yaw>1.5697565222072347</yaw>
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<q0>0.46294373924510057</q0>
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<q1>0.8476438715752446</q1>
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<q2>0.25765883963485936</q2>
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<q3>-0.028193680723036463</q3>
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<quality>PREDICT</quality>
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</radarPointingStateVector>
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</radarPointingStateVectorList>
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</LSAR>
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</radarPointing>

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