***Software Interface Specification (SIS) for the Lunar Prospector
Spectrometer Planetary Data System Files, Version V002***

***Los Alamos National Laboratory Report LAUR-99-2754***

***D. J. Lawrence^1^, S. Maurice^2^, and W. C. Feldman^1^***

***^1^Los Alamos National Laboratory, Los Alamos, NM, USA***

***^2^Observatoire Midi-Pyrénées, Toulouse, France***

This document is an addendum to the SIS document for the Version V001
submission of the Lunar Prospector spectrometer data (Los Alamos report
LAUR-99-2753). This data submission contains gamma-ray spectrometer
(GRS) data from Jan. 16, 1998 to Dec. 19, 1998 and neutron spectrometer
(NS) data from Jan. 16, 1998 to October 5, 1998. This document describes
changes that have been made to the data processing since the V001
submission. Detailed descriptions are given where changes have been made
to the data and/or processing. For headings where changes have not been
made, the reader is referred to the version V001 document.

**Spacecraft Spin Flip**: One major change between the V001 and V002
submissions is that the V002 submission is being divided up into two
different time-ordered data sets. This is because the LP spacecraft
executed a 180° flip of the spin axis on October 5, 1998 which continued
until October 7, 1998. Since the response functions of both the GRS and
NS vary according to latitude and spacecraft orientation, the pre-flip
and post-flip data is being handled separately. For the GRS, both pre-
and post-flip data are being submitted. For the NS, only pre-flip data
is being submitted at this time. An addendum to the V002 submission will
include the post-flip NS data. The exact times of the spin flip
maneuvers are being included in the V002 submission in the
*Auxiliary_V002.txt* data file.

**Leonid Meteor Shower:** For five days in November 1998 (Nov. 15 - Nov.
19), the spin orientation of the LP spacecraft was changed to minimize
damage by particles from the Leonid meteor shower. Since the spin axis
was not parallel to the Moon's spin axis at this time, data from this
period are not being included in the V002 submission. The times for this
maneuver are listed in the *Auxiliary_V002.txt* data file.

# 1. Gamma-Ray Spectrometer (GRS)

*1.1 Introduction*

The GRS data now contains four primary data files: the pre-flip files
are: *GRS_spectra_high1_V002.cdf* and *GRS_ThK_high1_V002.cdf*; the
post-flip files are *GRS_spectra_high2_V002.cdf* and
*GRS_ThK_high2_V002.cdf*. These files have the same format and
description as the similar V001 data files. The file:
*Auxiliary_V002.txt* contains the times of the spin flip maneuvers.

*1.2 GRS Data Contents: Integrated Spectra*

Same as the V001 submission.

*1.3 GRS Data Contents: Thorium and Potassium Counting Rates*

Same as the V001 submission.

*1.4 GRS Data Processing: Integrated Spectra*

The following processing steps have been done to create the GRS
integrated spectra.

**Deadtime:** Same as the V001 submission.

**Gain Corrections:** Same as the V001 submission. Updates of the GRS HV
gain change times are included in an auxiliary file.

**Solar Energetic Particle (SEP) Events:** Same as the V001 submission.
Updates of the SEP times are included in an auxiliary file.

**Galactic Cosmic Ray (GCR) Effects:** The correction for the GCR
variations has been modified in the following way. Instead of smoothing
the 6.13 MeV gamma-ray counting rate data over two hours, the 6.13 MeV
gamma-ray counting data is now averaged only for latitudes poleward of
±80°. This is being done to minimize composition effects that may have
been included in the previous GCR correction.

**Binning of Data:** Same as the V001 submission.

**Standard Deviation:** Same as the V001 submission.

**Height/Solid Angle Correction**: A correction is now being made to the
data to correct for variations in the Moon's solid angle seen by the
detector due to height variations. This correction is carried out by
assuming that the Moon is a sphere and calculating the fraction of a
half solid angle seen by the detector. This fractional solid angle is:

$$\Omega = \frac{q}{2p},$$

where,

$$q\text{=-}2p\text{cos}(\alpha - 1),$$

and,

$$\alpha = \text{sin}^{- 1}\left( \frac{R}{R + h} \right)\text{.}$$

Here, *R* = the mean lunar radius which is 1738 km, and *h* = the
spacecraft height above the mean lunar surface. All data is corrected to
a spacecraft height of 100 km.

$$$$

*1.5 GRS Data Processing: Thorium and Potassium Counts*

The following processing steps have been done to create the GRS thorium
and potassium counting rate data.

**Data Selection:** Same as the V001 submission.

**Latitude Correction:** The latitude correction is now a 6th polynomial
in sin(latitude):

$$f(x) = 1 + a_{1}\text{sin}(\lambda) + a_{2}\text{sin}^{2}(\lambda) + a_{3}\text{sin}^{3}(\lambda) + a_{4}\text{sin}^{4}(\lambda) + a_{5}\text{sin}^{5}(\lambda) + a_{6}\text{sin}^{6}(\lambda)$$

where the $a_{i}$ coefficients are different for the thorium and
potassium corrections.

**Binning of Data:** Same as the V001 submission.

**Standard Deviation:** Same as the V001 submission.

**Height/Solid Angle Correction**: The same height/solid angle
correction described in Section 1.4 was also carried out for the thorium
and potassium counting rate data.

*1.6 GRS Auxiliary Data File*

In addition to the counting rate data, the GRS data set contains an
auxiliary file in ASCII format: *Auxiliary_V002.txt*. The auxiliary file
contains two items for the GRS: times of solar energetic particle events
which have been omitted from the data; times of high voltage changes for
the GRS detector.

***2. Neutron Spectrometer (NS)***

*2.1 Introduction*

The NS data contains one primary data file: *NS_high1_V001.cdf*. The NS
data file contains counting rate data for thermal and epithermal
neutrons from Jan. 16, 1998 to October 5, 1998. This file contains only
pre-flip NS data. This file has the same format and description as the
similar V001 data file.

*2.2 NS Data Contents*

Same as the V001 submission.

*2.3 NS Data Processing*

The following steps have been done to create the NS neutron counting
rate data.

**Spacecraft Processing:** Same as the V001 submission.

**SEP Events:** Same as the V001 submission. Updates of the SEP times
are included in an auxiliary file.

**Galactic Cosmic Ray (GCR) Effects:** The correction for the GCR
variations has been modified in the following way. Instead of smoothing
the 6.13 MeV gamma-ray counting rate data over two hours, the 6.13 MeV
gamma-ray counting data is now averaged only for latitudes poleward of
±80°. This is being done to minimize composition effects that may have
been included in the previous GCR correction.

**Latitude Correction:** Same as the V001 submission.

**Height/Solid Angle Correction**: The same height/solid angle
correction described in Section 1.4 was also carried out for the thermal
and epithermal neutron counting rate data.

**Binning of Data:** Same as the V001 submission.

**Standard Deviation:** Same as the V001 submission.

*2.4 NS Auxiliary Data File*

Auxiliary data for the NS data is included in the file:
*Auxiliary_V002.txt*.

***3. Alpha Particle Spectrometer (APS)***

The APS data will be included as an addendum to the V002 submission.

***4. Common Data Format***

The V002 data is again being submitted in Common Data Format (CDF).
Future submissions may also include data in a raw binary format.

***5. Summary of Data Files for the V002 submission***

The following files make up the GRS and NS PDS Version V002 data
submission:

[Data files:]{.underline}

1.  Neutron data: pre-flip NS_high1_V002.cdf

2.  Gamma-ray spectrum: pre-flip GRS_spectra_high1_V002.cdf

3.  Gamma-ray spectrum: post-flip GRS_spectra_high2_V002.cdf

4.  Thorium and potassium data: pre-flip GRS_ThK_high1_V002.cdf

5.  Thorium and potassium data: post-flip GRS_ThK_high2_V002.cdf

6.  Auxiliary data Auxiliary_V002.txt

    [Content of data files:]{.underline}

7.  Neutron data: pre-flip NS_high1_V002-info.txt

8.  Gamma-ray spectrum: pre-flip GRS_spectra_high1_V002-info.txt

9.  Gamma-ray spectrum: post-flip GRS_spectra_high2_V002-info.txt

10. Thorium and potassium data: pre-flip GRS_ThK_high1_V002-info.txt

11. Thorium and potassium data: post-flip GRS_ThK_high2_V002-info.txt

***6. References***

There are no new references for the V002 submission.