LRS (Plasma Waves And Radio)¶

Of LRS (Lunar Radar Sounder), SOPRAN reads the public spectra (CDF) of the two receivers that measure natural radio and plasma waves.

Entry point	Receiver	Contents
`kg.lrs.npw`	NPW (Natural Plasma Wave)	Spectra of receivers 1 and 2
`kg.lrs.wfc`	WFC-H (Waveform Capture, high-frequency side)	Electric-field spectra plus gain, mode, and other support data

Variables¶

Entry point	Dimensions	Units	Meaning
`npw.rx1`, `npw.rx2`	`time, frequency`	dB	NPW spectra
`npw.mode`	`time`	flag	NPW mode
`wfc.ex_db`, `wfc.ey_db`	`time, frequency`	dB	Raw WFC spectra
`wfc.ex_field`, `wfc.ey_field`	`time, frequency`	dB uV/m	Field level after gain and band correction
`wfc.ex_power_spectral_density`, `wfc.ey_power_spectral_density`	`time, frequency`	(V/m)^2/Hz	Electric-field power spectral density
`wfc.gain`	`time`	dB	Gain decoded from the Gain flag
`wfc.mode`, `wfc.xymode`, `wfc.fband`, `wfc.omode`, `wfc.postgap`	`time`	flag	Raw Mode byte, the modes decoded from it, and the PostGap flag
`wfc.pdc_ti`, `wfc.pdc_ti_words`	`time` (`pdc_word`)	count	Spacecraft time counter (not UTC)

Names directly under the instrument, such as kg.lrs.wfc_ey_power_spectral_density, reach the same endpoints.

kg = spn.kaguya
time = spn.period("2008-04-01T00:00:00", "2008-04-01T02:00:00")

npw = kg.lrs.npw.rx1.load(time, missing="warn")
psd = kg.lrs.wfc.ey_power_spectral_density.load(time)

spn.stack(
    npw.spectrogram(y="frequency", log_color=True),
    psd.spectrogram(y="frequency", log_color=True),
    kg.lrs.wfc.gain.load(time).line(),
).plot()

Source files¶

NPW has one file per day and WFC one file per two hours. A range starting at an odd hour, such as 01:00–01:30, still reads the preceding 00:00 WFC file.

raw/kaguya/pds3/
  sln-l-lrs-5-npw-spectrum-v1.0/YYYYMMDD/data/LRS_NPW_V010_YYYYMMDD.cdf
  sln-l-lrs-4-wfc-spectrum-v1.0/YYYYMMDD/data/LRS_WFC_V010_YYYYMMDDhhmmss.cdf

Caching¶

LRS endpoints save what they read to the Store with cache="use" (default). Raw NPW and WFC spectra go to the normalized layer; gain, field level, power spectral density, and modes go to features. Reading the same period again does not reread the CDF. Results loaded with missing="empty" or "warn" while source files were missing are not saved.

Corrections and missing values¶

Field level and power spectral density follow the dB correction and bandwidth normalization of SPEDAS (kgy_lrs_load.pro) and lunarsat.
Values filled by the CDF sparse-record padding are kept distinct from observed zeros. For WFC support variables UINT1 254, and for PDC-TI [65534, 0, 65534], are treated as missing. These differ from the CDF FILLVAL=0.
Times come from the CDF Epoch (UTC). wfc_pdc_ti is a 48-bit on-board counter built from high, middle, and low 16-bit words; it is not converted to UTC without a conversion table. The raw three words stay in wfc_pdc_ti_words.

Limitations¶

Only WFC-H spectra can be read. WFC-L waveforms (10 Hz–100 kHz) are a separate product from the public spectra and are not supported.
There is no long-term comparison test with SPEDAS on real data yet.

Wave-event candidate extraction is in Experimental.

Sources¶

Y. Kasahara et al., "Plasma wave observation using waveform capture in the Lunar Radar Sounder on board the SELENE spacecraft," Earth, Planets and Space 60, 341–351 (2008). doi:10.1186/BF03352799
DARTS KAGUYA archive