Sean Solomon, Principal Investigator Date

David Jarrett, NASA Discovery Program Date

Manager

Deborah Domingue, Deputy Project Scientist Date

Doug Holland, Ground System Software Lead Date

Erick Malaret, SOC Manager Date

Raymond Arvidson, PDS Point of Contact Date

Max Peterson, Program Manager Date

Ralph McNutt, Project Scientist and Date

XRS Cognizant Co-I

Robert Nelson, Mission Operations System Date

Lead Engineer

Hien Nguyen, Ground Data System Date

Lead Engineer

Howard Taylor, SOC Lead Engineer Date

Bobby Williams, Navigation Date

Scott Murchie, MDIS Instrument Scientist Date Mark Robinson, MDIS
Cognizant Co-I Date

Noam Izenberg, MASCS Instrument Scientist Date William McClintock, MASCS
Date

Cognizant Co-I

Brian Anderson, MAG Instrument Scientist Date Mario Acuna, MAG Cognizant
Co-I Date

Barry Mauk, EPPS Instrument Scientist Date Robert Gold, EPPS Cognizant
Co-I Date

Xiaoli Sun, MLA Instrument Scientist Date David Smith, MLA & RS
Cognizant Co-I Date

Andrew Cheng, RS Instrument Scientist Date Richard Starr, XRS Instrument
Scientist Date

Released Date

##### 

##### **Table of Contents**

1\. Purpose and Scope of Document

2\. Overview of the MESSENGER Mission

2.1 Mission Operations Background

2.2 Mission Science Background

2.3 Ground Data System

3\. Definitions of Data Deliverables

3.1 Packetized Data Records

3.2 Standard Products

3.2.1 Experimental Data Records

3.2.2 Calibrated Data Records

3.2.3 Derived Data Products

3.2.4 Derived Analysis Products

3.3 Ancillary Products

3.3.1 Calibration Data

3.3.2 Navigation Products

3.3.3 Engineering Products

3.4 Documentation

3.5 Software

4\. Roles and Responsibilities

4.1 MESSENGER project

4.2 Planetary Data System

4.3 Johns Hopkins University/Applied Physics Laboratory

4.4 Carnegie Institution of Washington

4.5 Applied Coherent Technology

5\. Data Flow within the MESSENGER Project

5.1 Mission Operations Center

5.2 Navigation Team

5.3 Mission Design and G&C Team

5.4 Science Operations Center

5.5 Science Team

6\. Policies for Release of Data and Public Information

6.1 Data Rights and Release Policy

6.2 Public Information Release Policy

6.3 Release Policy to Science Community

6.4 Data Release Acknowledgment Policy

6.5 International Traffic in Arms Regulations (ITAR)

7\. Archive Process

7.1 Planning and Design

7.2 Generation

7.3 Validation

7.4 Delivery

8\. Definition of Terms

9\. References

10\. Arconyms

##### **1.0 Purpose and Scope of Document**

The MErcury Surface, Space ENvironment, GEochemisty, and Ranging
(MESSENGER) mission's Data Management and Science Analysis Plan (DMSAP)
presents a high-level strategy for the generation, validation, and
delivery of mission data and data products from the MESSENGER project's
Science Operations Center (SOC) to the Planetary Data System (PDS) in
complete, well-documented, and permanent archives. The plan also
specifies policies and procedures for distributing data and data
products within the MESSENGER project and to the science community and
general public.

This document is to be used by personnel associated with the MESSENGER
project to understand the roles and responsibilities of the MESSENGER
project, the MESSENGER SOC, and the PDS. Investigators associated with
MESSENGER will use this document to understand what is expected of them
in terms of delivery of a complete data archive, and how the SOC and PDS
can help them prepare their data products. PDS personnel will use this
document to understand the types and volumes of data products they can
expect to receive from the MESSENGER project.

![](media/image2.png)

**Figure 1. Mission Time Line**

**2.0 Overview of the MESSENGER Mission**

**2.1 Mission Operations Background**

The MESSENGER mission is designed to orbit Mercury following two flybys
each of Venus and Mercury. The overall timeline for the mission is given
in Figure 1. MESSENGER uses two gravity assists from Venus and two from
Mercury to pick up most of the change in velocity it needs to match
speed and orbital parameters with Mercury before orbit insertion. During
its two flybys of Mercury, MESSENGER will map nearly the entire planet
in color, image most of the part of the planet unseen by Mariner 10, and
take reconnaissance measurements of the composition and structure of the
surface, atmosphere, and magnetosphere.

MESSENGER's nominal orbit about Mercury is highly elliptical, 200 km
above the surface at its lowest point (periapsis) and over 15,000 km at
its highest point. The plane of the orbit is inclined 80° to Mercury\'s
equator, and the initial periapsis is at the latitude of 60°N. During
the Earth year of operations, solar perturbations cause an upward drift
in periapsis elevation (corrected three times) and a northward drift in
periapsis latitude (not corrected).

MESSENGER's propulsion system is integrated into the spacecraft
structure, making economical use of mass. The miniaturized instruments
are mostly co-located on a science deck facing Mercury, while the
spacecraft is shielded from direct sunlight by a lightweight sunshade.
Most of the instruments are fixed-mounted, so that coverage of Mercury
is obtained by spacecraft motion over the planet. The imaging system
uses a pivot platform to accommodate flyby imaging and optical
navigation, as well as variable look geometries for imaging during the
orbital phase.

Further information on MESSENGER mission and spacecraft design may be
found in Santo et al. (2001).

Table 1. MESSENGER payload and personnel

+-----------------------------------+------------------+--------------+
| **Instrument**                    | **Science Team   | **PDS Node   |
|                                   | Points of        | Contact**    |
|                                   | Contact**        |              |
+-----------------------------------+------------------+--------------+
| *Mercury Dual Imaging System      | IS: Scott        | Imaging Node |
| (MDIS)*                           | Murchie,         | (I)          |
|                                   | JHU/APL,         |              |
| Narrow-angle imager and           | scott.mu         | Eric Eliason |
| wide-angle multispectral imager.  | rchie@jhuapl.edu | (eelias      |
| Pointing is assisted with a pivot |                  | on@usgs.gov) |
| platform. Maps landforms, surface | Deputy IS:       |              |
| spectral variations, and          | Louise Prockter, |              |
| topographic relief from stereo    | JHU/APL,         |              |
| imaging.                          | louise.pro       |              |
|                                   | ckter@jhuapl.edu |              |
|                                   |                  |              |
|                                   | Co-I: Mark       |              |
|                                   | Robinson,        |              |
|                                   | Northwestern     |              |
|                                   | University,      |              |
|                                   | robins           |              |
|                                   | on@earth.nwu.edu |              |
+-----------------------------------+------------------+--------------+
| *Gamma-Ray and Neutron            | IS: Edgar        | Geoscience   |
| Spectrometer (GRNS)*              | Rhodes, JHU/APL, | Node (GS)    |
|                                   |                  |              |
| Gamma-Ray Spectrometer (GRS)      | Deputy IS: Larry | Ed Guinness  |
| measures the emissions from       | Evans, GSFC,     | (gu          |
| radioactive elements and          | larry.eva        | inness@wunde |
| gamma-ray fluorescence stimulated | ns@gsfc.nasa.gov | r.wustl.edu) |
| by cosmic rays. Used to map       |                  |              |
| elemental abundances in crustal   | Co-I: William    |              |
| materials.                        | Boynton,         |              |
|                                   | University of    |              |
| Neutron Spectrometer (NS)         | Arizona,         |              |
| provides sensitivity to hydrogen  | wboynton@gamma1  |              |
| in ices at the poles and average  | .lpl.arizona.edu |              |
| sub-spacecraft atomic weight of   |                  |              |
| crustal material.                 |                  |              |
+-----------------------------------+------------------+--------------+
| *X-Ray Spectrometer (XRS)*        | IS: Richard      | Geoscience   |
|                                   | Starr, GSFC,     | Node (GS)    |
| Measures the fluorescence in      | richard.sta      |              |
| low-energy X-rays that is         | rr@gsfc.nasa.gov | Ed Guinness  |
| stimulated by solar gamma rays    |                  | (gu          |
| and high-energy X-rays. Used to   | Deputy IS:       | inness@wunde |
| map elemental abundances of       | George Ho,       | r.wustl.edu) |
| crustal materials                 | JHU/APL,         |              |
|                                   | geor             |              |
|                                   | ge.ho@jhuapl.edu |              |
|                                   |                  |              |
|                                   | Co-I: Ralph      |              |
|                                   | McNutt, JHU/APL, |              |
|                                   | ralph.m          |              |
|                                   | cnutt@jhuapl.edu |              |
+-----------------------------------+------------------+--------------+
| *Magnetometer (MAG)*              | IS: Brian        | Planetary    |
|                                   | Anderson,        | Plasma       |
| Maps out the detailed structure   | JHU/APL,         | Interactions |
| and dynamics of Mercury\'s        | brian.and        | Node (PPI)   |
| magnetic field and searches for   | erson@jhuapl.edu |              |
| regions of magnetized crustal     |                  | Steve Joy    |
| rocks.                            | Co-I: Mario      |              |
|                                   | Acuña, GSFC,     | (sjoy@ig     |
|                                   | mha@lepm         | pp.ucla.edu) |
|                                   | on.gsfc.nasa.gov |              |
+-----------------------------------+------------------+--------------+
| *Mercury Laser Altimeter (MLA)*   | IS: Xiaoli Sun,  | Geoscience   |
|                                   | GSFC             | Node (GS)    |
| An infrared laser transmitter     |                  |              |
| coupled with a receiver that      | xiaoli.s         | Ed Guinness  |
| measures the round-trip time of a | un@gsfc.nasa.gov | (gu          |
| burst of laser light reflected    |                  | inness@wunde |
| off Mercury\'s surface, yielding  | Deputy IS:       | r.wustl.edu) |
| a distance measurement. Produces  | Andrew Cheng,    |              |
| highly accurate measurements of   | JHU/APL,         |              |
| topography, and measures          | andy.            |              |
| Mercury\'s physical libration.    | cheng@jhuapl.edu |              |
|                                   |                  |              |
|                                   | Co-I: David E.   |              |
|                                   | Smith, GSFC,     |              |
|                                   | dsmith@thars     |              |
|                                   | is.gsfc.nasa.gov |              |
+-----------------------------------+------------------+--------------+
| *Mercury Atmospheric and Surface  | IS: Noam         | Atmospheres  |
| Composition Spectrometer (MASCS)* | Izenberg,        | Node (A)     |
|                                   | JHU/APL,         |              |
| Ultraviolet-Visible Spectrometer  | noam.ize         | Lyle Huber   |
| (UVVS) measures composition and   | nberg@jhuapl.edu | (lhub        |
| spatial and temporal variations   |                  | er@nmsu.edu) |
| of exospheric species.            | Co-I: William    |              |
|                                   | McClintock,      |              |
| Visible-Infrared Spectrograph     | LASP,            |              |
| (VIRS) maps surface reflection to | william.mcclint  |              |
| determine mineral composition.    | ock@colorado.edu |              |
+-----------------------------------+------------------+--------------+
| *Energetic Particle and Plasma    | IS: Barry Mauk,  | Planetary    |
| Spectrometer (EPPS)*              | JHU/APL,         | Plasma       |
|                                   | <barry.          | Interactions |
| Measures the composition, spatial | mauk@jhuapl.edu> | Node (PPI)   |
| distribution, energy, and         |                  | Steve Joy    |
| time-variability of charged       | Deputy IS:       | (sjoy@ig     |
| particles within and surrounding  | Stefano Livi,    | pp.ucla.edu) |
| Mercury\'s magnetosphere. Plasma  | JHU/APL,         |              |
| is measured by the Fast Imaging   | <stefano.        |              |
| Plasma Spectrometer (FIPS) and    | livi@jhuapl.edu> |              |
| higher-energy particles by the    |                  |              |
| Energetic Particle Spectrometer   | Deputy IS:       |              |
| (EPS)                             | Thomas           |              |
|                                   | Zurbuchen,       |              |
|                                   |                  |              |
|                                   | t                |              |
|                                   | homasz@umich.edu |              |
|                                   |                  |              |
|                                   | Co-I: Robert     |              |
|                                   | Gold, JHU/APL,   |              |
|                                   | rob              |              |
|                                   | .gold@jhuapl.edu |              |
+-----------------------------------+------------------+--------------+
| *Radio Science (RS)*              | IS: Andrew       | Radio        |
|                                   | Cheng, JHU/APL,  | Science Node |
| Uses the Doppler effect (the      | andy.            | (RS)         |
| shift in the frequency of the     | cheng@jhuapl.edu |              |
| spacecraft\'s radio signal with   |                  | Dick Simpson |
| changes in the spacecraft\'s      | Co-I: David E.   | (rsimpso     |
| velocity relative to Earth) to    | Smith, GSFC,     | n@magellan.s |
| measure Mercury\'s mass           | dsmith@thars     | tanford.edu) |
| distribution, including spatial   | is.gsfc.nasa.gov |              |
| differences in crustal thickness, |                  |              |
| and corresponding gravitational   |                  |              |
| field.                            |                  |              |
+-----------------------------------+------------------+--------------+
| *Navigation*                      | Bobby Williams,  | Navigation   |
|                                   | JPL,             | and          |
|                                   | bobby.willi      | Ancillary    |
|                                   | ams@jpl.nasa.gov | Information  |
|                                   |                  | Node (NAIF)  |
|                                   |                  |              |
|                                   |                  | Chuck Acton  |
|                                   |                  | (charl       |
|                                   |                  | es.h.acton@j |
|                                   |                  | pl.nasa.gov) |
+-----------------------------------+------------------+--------------+
| *Engineering*                     | Robert Nelson,   | Navigation   |
|                                   | JHU/APL,         | and          |
|                                   | robert.n         | Ancillary    |
|                                   | elson@jhuapl.edu | Information  |
|                                   |                  | Node (NAIF)  |
|                                   |                  |              |
|                                   |                  | Chuck Acton  |
|                                   |                  | (charl       |
|                                   |                  | es.h.acton@j |
|                                   |                  | pl.nasa.gov) |
+-----------------------------------+------------------+--------------+

IS -- Instrument Scientist, Co-I listed is the cognizant Co-I.

**2.2 Mission Science Background**

As described in the Concept Study Report (CSR) and Solomon et al.
(2001), MESSENGER is a scientific Discovery mission whose goal is to
answer focused science questions using an optimized set of miniaturized
instruments: What is the origin of Mercury\'s high density? What are the
composition and structure of its crust? What is the nature of its core?
What is Mercury\'s tectonic history, and has its surface been shaped by
volcanism? What are the characteristics of the exosphere and miniature
magnetosphere? And what is the nature of the mysterious near-polar
deposits? These questions have been formalized in the MESSENGER Concept
Study Report (CSR). The questions have been mapped to a set of MESSENGER
objectives, which are in turn mapped to measurement objectives (the
MESSENGER objectives are captured in Section 2.1.2 of the Program Level
Requirements (PLR)).

The science payload for MESSENGER is listed in Table 1. Further
information may be found in Gold et al. (2001). The science questions
generate measurement objectives for the payload, which flow down to
requirements for instrument capabilities and for derived data products,
and eventually to science results that provide closure to the mission
science objectives (cf. PLR § 2.2). Table 1 also gives, for each
instrument, the Co-Investigator(s) cognizant of the measurement
objectives and associated derived data and analysis products, and the
Instrument Scientist(s) cognizant of the instrument hardware, software,
performance, and calibration requirements.

Although Table 1 lists a PDS Node Contact for each of the instruments,
Raymond Arvidson of Washington University is the MESSENGER PDS Point of
Contact.

**2.3 Ground Data System**

The MESSENGER Ground Data System (GDS) will convert the raw spacecraft
data stream to science data products. The Mission Operations Center
(MOC), located at The Johns Hopkins University/Applied Physics
Laboratory (JHU/APL), will be responsible for monitoring and commanding
the spacecraft and payloads and coordinating real‑time mission planning.
The MOC receives planetary and spacecraft ephemerides from the
Navigation Team, in addition to light time files and tracking requests.
The Mission Design and G&C Team supply orbital maneuver information and
parameters to the MOC. All payload commanding is generated by the SOC
and transferred to the MOC for implementation. The MOC will receive
telemetry packets from the Deep Space Network (DSN) and process them
through CODMAC (Committee On Data Management And Computation) Level 1
(see Table 2 for CODMAC data Level definitions), providing the CODMAC
Level 1 data to the SOC. Navigation data, including spacecraft and
planetary ephemerides, and spacecraft pointing data, will be transmitted
to the SOC in SPICE format.

The SOC will coordinate all data acquisition, planning, and instrument
operations, and will support the MESSENGER Science Team in the
processing and analysis of the science data. It will provide easy access
to all the data required by the Science Team and the MOC. The SOC will
accept and process telemetry, command history, and navigation data
through CODMAC Level 1, creating CODMAC Level-2 Experiment Data Records
(EDRs), calibration files, and a telemetry archive. The SOC will archive
the Level 1 and 2 data with PDS.

The Science Team is responsible for science data processing through
CODMAC Levels 3 through 5 and for delivering these products to the SOC
in PDS-standard formats including associated documentation, as outlined
in each instrument's Software Interface Specification (SIS) documents
and the Archive Generation, Validation, and Dissemination Plan (AGVDP).
The SOC is responsible for negotiating with the PDS all product formats
and delivery of all data products to the PDS. The Science Team will also
generate science priorities for flyby encounter activities and in-flight
tests, with the science sequence planning coordinated through the SOC.

The roles and responsibilities of the MOC, SOC, and Science Team are
discussed in more detail in Section 4.1. A description of the data flow
within the MESSENGER project is provided in Section 5.

**Table 2. CODMAC/NASA definition of processing levels for science data
sets**

  ---------- --------------- -----------------------------------------------
  **NASA**   **CODMAC**      **Description**

  Packet     Raw - Level 1   Telemetry data stream as received at the ground
  data                       station, with science and engineering data
                             embedded. Referred to in this document as
                             Packetized Data Products (PDRs).

  Level 0    Edited - Level  Instrument science data (e.g., raw voltages,
             2               counts) at full resolution, time ordered, with
                             duplicates and transmission errors removed.
                             Referred to in this document as Experimental
                             Data Records (EDRs).

  Level 1A   Calibrated -    NASA Level 0 data that have been located in
             Level 3         space and may have been transformed (e.g.,
                             calibrated, rearranged) in a reversible manner
                             and packaged with needed ancillary and
                             auxiliary data (e.g., radiances with the
                             calibration equations applied). Referred to in
                             this document as Calibrated Data Records
                             (CDRs). In some cases, these also qualify as
                             derived data products (DDPs).

  Level 1B   Resampled -     Irreversibly transformed (e.g., resampled,
             Level 4         remapped, calibrated) values of the instrument
                             measurements (e.g., radiances, magnetic field
                             strength). Referred to in this document as
                             either derived data products (DDPs) or derived
                             analysis products (DAPs).

  Level 1C   Derived - Level NASA Level 1A or 1B data that have been
             5               resampled and mapped onto uniform space-time
                             grids. The data are calibrated (i.e.,
                             radiometrically corrected) and may have
                             additional corrections applied (e.g., terrain
                             correction). Referred to in this document as
                             derived analysis products (DAPs).

  Level 2    Derived - Level Geophysical parameters, generally derived from
             5               Level 1 data, and located in space and time
                             commensurate with instrument location,
                             pointing, and sampling. Referred to in this
                             document as derived analysis products (DAPs).

  Level 3    Derived - Level Geophysical parameters mapped onto uniform
             5               space-time grids. Referred to in this document
                             as derived analysis products (DAPs).

             Ancillary Data  Non-science data needed to generate calibrated
             -- Level 6      or resampled data sets and consisting of
                             instrument gains, and offsets, spacecraft
                             positions, target information, pointing
                             information for scan platforms, etc.
  ---------- --------------- -----------------------------------------------

The above is based on the National Research Council Committee on Data
Management and Computation (CODMAC) data levels.

**3. Definitions of Data Deliverables**

The science-related data products to be produced during the MESSENGER
mission are described in this section, including standard products,
engineering and other ancillary products, and documentation that
accompanies data sets as they are delivered to the PDS. Table 2 defines
numerical processing levels as defined by the National Research Council
CODMAC.

**3.1 Packetized Data Records (PDRs)**

These data records consist of packetized telemetry that is received from
the spacecraft with science and engineering data embedded. PDRs have
duplications removed and include any ancillary information needed to
understand what is contained in a given packet (e.g., instrument data
vs. spacecraft health information). These are CODMAC Level-1 data
produced by the MOC and delivered to the SOC for production of EDRs.
PDRs are not archived to the PDS.

**3.2 Standard Products**

Standard products are CODMAC Level-2 (See Table 2) and higher science
data products. The MESSENGER science data are divided into two
categories: Level-2 raw data (referred to as experimental data records
or EDRs) and processed data (referred to as reduced data records or
RDRs). RDRs are generated from EDRs, and represent either data
calibrated to a physical unit such as radiance (Level-3), resampled
Level-4 data products, or derived Level-5 data products. RDR standard
products are produced primarily by discipline groups on the Science Team
(see Sec. 4 Roles and Responsibilities).

The RDRs are subdivided into three groups: calibrated data records
(CDRs), derived data products (DDPs), and derived analysis products
(DAPs). Tables 3 and 4, taken from the MESSENGER CSR, lists the DDPs and
DAPs which the project is responsible for delivering to the PDS to
archive. All standard products will be delivered to the Planetary Data
System in PDS-compliant format, including PDS labels and documentation.
The documentation shall be sufficiently thorough for users to understand
the processing history.

**Table 3. Derived Data Products** (taken from CSR Table D-2-9)

  ------------ ----------------------------- ------------ ------------ ------------
  **System**   **Data Product**              **Team\***   **Lead**     **CODMAC
                                                                       Level**

  MDIS         Catalogued images             GG           Murchie      3,4

  GRNS         γ-ray spectra, neutron flux   GC           Boynton      3,4

  MAG          **B**-field vectors           AM           Anderson     3,4

  MLA          Range profiles, radiometry    GP           Zuber        3,4

  MASCS/ UVVS  Limb tangent height spectra   AM           McClintock   3,4

  MASCS/ VIRS  Surface reflectance spectra   GC           McClintock   3,4

  EPPS         Particle energy vs.           AM           Gold         3,4
               composition vs. angle                                   
               distributions                                           

  XRS          X-ray spectra                 GC           Trombka      3,4

  RS           Doppler data, ranging data,   GP           Smith        3,4
               occultation times                                       
  ------------ ----------------------------- ------------ ------------ ------------

\* GG: Geology Group, GC: Geochemistry Group, GP: Geophysics Group, AM:
Atmosphere and Magnetosphere Group.

**Table 4. Derived Analysis Products** (taken from CSR Table D-1-1)

  ----------------------- -------------------------------- ---------------
  **SYSTEM**              **ANAYLSIS PRODUCT**             **CODMAC
                                                           Level**

  GRNS, XRS               Global element map               5

  MDIS, MASCS             Spectral unit map                5

  MDIS                    Global monochrome map            5

  MDIS                    Stereo maps                      5

  MDIS                    Multispectral image catalogue    5

  MLA                     North-hemisphere topography map  5

  MLA                     Altimetric profiles              5

  RS                      North-hemisphere gravity model   5

  MAG                     Multipole internal magnetic      5
                          field model                      

  MAG, EPPS               Time-dependent magnetosphere     5
                          model                            

  MLA, RS                 Libration amplitude              5

  MLA, RS                 RA and DEC of Mercury's          5
                          rotational pole                  

  RS                      Spherical harmonic gravity field 5

  RS                      Low-degree global shape          5

  MLA                     North-hemisphere topographic     5
                          profiles                         

  MASCS                   Exosphere model                  5

  MASCS, EPPS, GRNS, XRS  Volatile species and sources     5
  ----------------------- -------------------------------- ---------------

**3.2.1 Experimental Data Records**

Raw data or EDRs consist of unprocessed instrument-count data including
a description of the observation geometry (boresight, spacecraft, and
target). In those cases where on-board compression has been applied, the
EDRs contain the unmodified compressed instrument data as downlinked to
the SOC through the Deep Space Network (DSN). Compressed and
decompressed versions of these EDRs will be delivered to the PDS as
CODMAC Level-2 data. Decompressed EDRs will be supplied to the Science
Team by the SOC for science analysis purposes. Calibrated Data Records,
discussed in the following section, are EDRs which have been
decompressed and radiometrically calibrated and are CODMAC Level-3
archive products. Each instrument EDR is formatted to include standard
PDS labels (instrument count data are otherwise unprocessed). To make
full scientific utilization of the archived EDR data, processing such as
decompression, radiometric calibration, and geometric rectification may
be necessary. A brief description of each instrument's EDR follows.
Detailed descriptions can be found in each instrument's SIS document.

*MDIS*

Each camera observation results in one to five image products processed
on board the spacecraft. The image product may contain the entire image
frame or up to five sub-frames. All image products are compressed and
stored on the Solid State Recorder (SSR) for downlink to the DSN and
then to the SOC. Each image product is stored as an array of lines
(rows) and samples (columns) where the array values correspond to raw
instrument counts (data numbers, DNs).

*GRS*

When a gamma ray or cosmic ray interacts with the Ge semiconductor
detector, a charge is generated. The amount of charge is proportional to
the energy deposited. When a gamma ray or cosmic ray interacts with the
borated plastic scintillator shield surrounding the bottom and sides of
the Ge detector, a light pulse is generated that is converted to a
voltage pulse by a photomultiplier. The pulse magnitude is proportional
to the energy deposited. The amount of charge is measured and then
converted into the appropriate channel number, which is proportional to
energy. Each GRS observation results in three spectra. The three spectra
are described as: (1) all interactions in the primary Ge detector, the
raw Ge spectrum; (2) all interactions in the plastic shield, the plastic
spectrum; (3) all interactions in the primary Ge detector that are not
in coincidence with an interaction in the plastic shield, the Ge
anticoincidence spectrum. The first and third spectra are binned into
16384 channels, and the second spectrum is binned into 1024 channels.
The distribution of energy deposition as a function of energy (channel
number) is recorded over a commanded integration time period. Each EDR
is a histogram of the number of events in each channel over the
integration period and is designated as a single spectrum.

*NS*

The MESSENGER NS EDRs consist of five spectra plus event-mode data.
These EDRs are generated as follows. The MESSENGER NS consists of a
sandwich of three scintillators that are optically decoupled from each
other. The first and third scintillators are lithium-glass
scintillators, which respond to a combination of thermal and epithermal
neutrons that span the range between 0 eV and about 1 keV. Each of these
scintillators generates a neutron spectrum (or histogram). When a
thermal or epithermal neutron interacts with one of these scintillators
a charge is generated. The charge is converted into one of 32 channels,
which are correlated to energy. Over a commanded integration time period
the distribution of events (neutron encounters) as a function of energy
(channel number) is recorded. The result is a histogram of the number of
events in each channel accumulated over the integration period, which is
designated as a single neutron spectrum. Two such spectra are produced,
one by each lithium-glass scintillator.

The center scintillator is a borated plastic (BP) scintillator.
Time-correlated events in the BP scintillator provide a measure of the
flux of fast neutrons (0.5 MeV \< E \< 7 MeV). These events are defined
by a time-correlated pair of interactions in the BP scintillator. The
first interaction corresponds to a neutron that loses all of its
sensible energy in the BP scintillator, and the second interaction
corresponds to the energy released by the ^10^B(n,α)^7^Li reaction. The
signature of the time-correlated events includes the pulse height
(correlated to energy) of the first interaction (called a prompt energy,
E~p~), the pulse height that corresponds to the Q-value of the
^10^B(n,α)^7^Li reaction (called the capture energy, E~c~), and the time
between first and second interactions (or Time To Second Pulse, TTSP).
When a fast neutron interacts with the BP scintillator a charge is
generated corresponding to E~p~. The charge is converted into one of 64
channels, which are correlated to energy. Over a commanded integration
time period the distribution of E~p~ events as a function of energy
(channel number) is recorded. The result is a histogram of the number of
E~p~ events in each channel accumulated over the integration period,
which is designated as a single neutron spectrum. The event-mode data
(E~p~, E~c~, and TTSP) are also converted into histograms. Over the
integration time period the number of events with a given TTSP are
counted. The results are two histograms, or spectra. The first histogram
is the number of time-correlated events as a function of TTSP for TTSP
values ranging from 0 to 0.4 μs. The second histogram is the number of
time-correlated events as a function of TTSP for TTSP values ranging
from 0.4 μs to 25.6 μs. In addition to the five spectra described above,
the NS EDRs include a precommanded subset of the event-mode data (E~p~,
E~c~, and TTSP values).

*XRS*

Each XRS observation results in four X-ray spectra. When an X-ray
interacts with one of the four detectors, a charge or voltage pulse is
generated. This signal is converted into one of 2^8^ (256) channels,
which are correlated to energy. Over a commanded integration time period
the distribution of events (X-ray encounters) as a function of energy
(channel number) is recorded. The EDRs are the number of events in each
channel of the four detectors accumulated over the integration period.
The result is four 256-channel histograms, each of which is designated
as a single X-ray spectrum.

*MASCS/VIRS*

The VIRS portion of the MASCS instrument measures surface reflectance in
the wavelength range 0.3 to 1.45 μm. VIRS detectors collect photons from
the MASCS telescope. A flat field, concave holographic grating disperses
and images the fiber aperture onto two linear array detectors. Located
near the spectrograph focal plane is a dichroic beam splitter, which
separates visible and infrared wavelengths before they are imaged onto
the two detectors. The detectors consist of a silicon 512-element array
covering the wavelength range 300-1050 nm (using \~320 pixels) and an
Indium Gallium Arsenide (InGaAs) 256-element detector covering 850-1450
nm (using all pixels). The spectral bandpass is approximately 5 nm over
the entire wavelength range. Photons incident on the detectors generate
electrons, which are counted and converted to DN using an electron to DN
analog-to-digital conversion factor. Both detectors are digitized to 16
bits and are stored as discrete spatial measurements onboard the SSR in
compressed format (lossy and lossless options) for transmission to
Earth. A VIRS EDR is an array comprising a single spectrum with
associated temperature monitor data and instrument telemetry. Spectra
can have acquisition times ranging from 50 ms to several seconds.
Nominal acquisition time is 1 s/spectrum. VIRS EDRs will thus consist of
two sets (one for each detector) of discrete spatial measurements
totaling 576 elements using 16-bit words per element.

*MASCS/UVVS*

The UVVS portion of the MASCS instrument consists of three
photo-multiplier tube (PMT) detectors sensitive across the wavelength
range (115 to 600 nm) with a spectral resolution of \~ 1 nm. The Far UV
tube is for 115-190 nm light in 0.5-nm steps (2nd order), the Mid UV
tube is for wavelengths 160-320 nm in 1-nm steps, and the Vis tube is
250-600 nm in 1-nm steps. Light is collected by a telescope and fed to
the spectrometer via an entrance slit. The grating disperses the light
as a function of wavelength and, as the grating is scanned, light over a
specified wavelength interval falls on one of three exit slits. The exit
slits are spatially positioned so that light from each of the three
wavelength ranges given above falls on one of the exit slits. Each exit
slit leads to one of the PMTs, thus allowing each PMT to count over its
specified wavelength range. The PMTs operate in pulse-counting mode and
collect photons for a specified integration time. Incoming photons to a
PMT hit the photocathode and generate electrons, which are directed
toward dynode strings where they multiply. At the end of the tube a
pulse amplifier discriminator (PAD) amplifies the electrical signal
received and compares against a threshold value to determine whether to
send out a count. A UVVS atmospheric profile EDR is a series of
accumulated counts at different grating positions. The grating position
and integration time are determined by instrument command. The resulting
spectra, which may have variable length, are stored as single line
arrays of values that correspond to counts per wavelength. UVVS EDRs
will thus consist of three sets (one for each detector) of discrete
spatial measurements across their respective wavelengths.

*EPPS/EPS*

EPS observes energetic charged ions and electrons and discriminates them
by energy, angle of arrival, and mass species (electrons and ion mass
composition). The sample space may be represented as a 3-dimensional
Cartesian coordinate system with one axis representing energy, a second
axis representing species (electrons and ion mass composition), and the
third axis representing angle of arrival (derived by determining which
of six detectors was stimulated by the particle). The mass axis includes
positions where mass is not determined cleanly. The several hundred data
channels in the EDR consist of the rates (in counts per time
accumulation) of detected charged particles that occupy several hundred
boxes defined within the 3-dimensional sample space. At any one time,
different groupings of boxes are sampled with different accumulation
times. At any one time, two separate and overlapping groupings of
channels may be sampled, each with their own set of accumulation times,
representing high- and medium- priority data. Channel accumulations
times range from \~300 s to \~0.5 s depending on orbital position. All
channel rates are compressed to 10 bits with a log compression scheme. A
separate data stream consists of full pulse-height analysis data (PHA)
for each of a small subset of individual particles that are detected.
The properties of each captured particle are represented in 48-bit words
with full PHA information available for energy and particle velocity,
yielding high-resolution energy and mass species discrimination.

*EPPS/FIPS*

FIPS also observes charged ions (not electrons) but over a different
range of energies. The sample space for FIPS has one more dimension than
does EPS because FIPS performs angle sampling in 2 dimensions rather
than just one. The sample space consists of: energy/charge, mass/charge,
angle_x, and angle_y. The data channels again consist of the particles
per accumulation period that occupy various boxes within the
4-dimensional sample space. Again, different groupings of channels are
sampled with various accumulation periods, and two different groupings
of channels may be sampled simultaneously, representing high- and
medium-priority data. All channel rates are compressed to 8 or 10 bits
using a log compression scheme. Again, a separate data stream consists
of full PHA information (28 bits) about a small subset of the individual
particles that are detected. In the case of FIPS, the PHA data yield
high-resolution information concerning the mass species distributions
and the angles of arrival.

*MAG*

The magnetometer records the vector (X, Y and Z axes) magnetic field at
the location of the sensor at the tip of the 3.6-meter-long magnetometer
boom. The instrument samples internally at 20 samples per second and
depending on science objectives and telemetry availability will be
commanded to provide output for telemetry at selected rates of 0.01/s,
0.02/s, 0.05/s, 0.1/s, 0.2/s, 0.5/s, 1/s, 2/s, 5/s, 10/s, and 20/s. The
nominal rate in orbit is expected to be 1/s. All three axes are output
for telemetry at the same rate. The instrument is equipped with two
sensitivity ranges, ±65,536 nT (2 nT least significant bit, LSB) and
±1024 nT (0.03 nT LSB), appropriate for pre-launch testing in Earth's
field and science observations at Mercury, respectively. The low
sensitivity range also provides added dynamic range in case unexpectedly
strong crustal fields are present at Mercury.

The MAG EDRs consist of time-ordered series of counts of the X, Y, and Z
components, and one field-fluctuation measurement channel (AC level).
The AC level is the average absolute value of the 1-10 Hz-filtered
magnetic field data. It is a log-compressed 8-bit value (4-bit exponent,
4-bit mantissa) and is also referred to as 'logAC'. Only one axis,
selectable by command, is used to evaluate the fluctuation level. The AC
level is reported at most once every second. In rates 2/s, 5/s, 10/s,
and 20/s the AC level is reported once every second. At lower output
rates, the AC level is reported at the commanded output rate.

Three types of MAG EDRs are produced: low-rate housekeeping (MAG-LHK2),
standard science data (MAG-SSD2), and burst data (MAG-BST2), where the
integer at the end of the data type denotes data level. The EDRs for
each type are self contained, independent records.

The MAG-LHK2 records provide low volume, complete orbital coverage of
health and safety data and low-time-resolution (50 s, 500 s, or 2000 s
between readings) magnetic field and fluctuation level readings. It is
designed for daily downlink from the spacecraft to monitor instrument
health and provide full-orbit coarse-time-resolution data coverage for
mission planning and data survey purposes. On-orbit low-rate
housekeeping mode (LHK) will be operated at 50-s sampling between
magnetic field samples. During cruise LHK will be operated at 500 s or
2000 s between magnetic field samples. MAG-LHK2 data are uncompressed.
Each MAG-LHK2 record consists of a header that includes a start time
tag, LHK sample rate, instrument range, primary health and safety data
for MAG (electronics and probe temperatures and electronics current),
instrument status flags and 10 XYZ field samples, 10 AC levels, and 10
corresponding delta-time tags providing 0.05-s time knowledge relative
to the header time tag. Sequential MAG-LHK2 records will comprise a
continuous time record. Records with fewer than 10 samples can occur if
the instrument is commanded to or autonomously invokes a terminate-LHK
packet command. In case of packet termination, no interruption of
continuity occurs since the subsequent new LHK packet picks up the time
sequence.

The MAG-SSD2 record provides the primary science MAG data and consists
of XYZ samples and AC level values at the commanded sample rate. The
standard science data (SSD)will be used for detailed science analysis of
Mercury's intrinsic magnetic field and of its magnetospheric
configuration and dynamics. Each MAG-SSD2 record consists of a header
that includes a time tag providing 0.05-s precision, instrument range,
sample rate, compression flag (ON/OFF), compression bit length for each
axis (XYZ), and 200 XYZ samples together with 200 or fewer AC level
samples (see above). The first XYZ sample is uncompressed, and the
remaining samples are compressed as differences from the preceding
sample using the bit length indicated in the header. Compression of
magnetic field values in SSD records may be commanded on or off.
Typically compression will be used. Sequential MAG-SSD2 records will
comprise a continuous time record. Records with fewer than 200 samples
can occur if the instrument is commanded to or autonomously invokes a
terminate-SSD packet command. In case of packet termination, no
interruption of continuity occurs since the subsequent new SSD packet
picks up the time sequence.

The MAG-BST2 records provide snapshots of 20/s vector samples, or
'burst' sampling, over a time span of 8 minutes, a total of 9600 vector
samples for each burst interval. The burst data provide information
about waves and turbulent phenomena expected to occur at the
magnetospheric boundaries and elsewhere in association with pickup
processes of volatile species as they are photo-ionized. Each snapshot
consists of 15 MAG-BST2 time-contiguous records. Data are recorded at
20/s during a commanded time window when the AC level exceeds a
commanded trigger level. The number of bursts to record in each window
is also commanded and will typically be 1. MAG-BST2 records consist of a
header including instrument range, time tag providing 0.05 s precision,
and compression bit length for each axis (XYZ). MAG-BST2 data are always
compressed. The body of the data consists of 640 XYZ samples at 20/s
sampling rate. The first sample is uncompressed, and the remaining 639
samples are compressed as differences from the preceding sample using
the bit length indicated in the header. The 15 MAG-BST2 records comprise
a continuous time series spanning the 8-minute burst. Typically one
burst period will be recorded every day.

*MLA*

The MLA is a direct-detection, time-of-flight laser altimeter that
determines the range from the spacecraft to the surface of Mercury by
measuring the round-trip travel time of laser pulses. The file formats
for the downlinked data include a primary header, a secondary header,
user data, and instrument status. The EDRs take the form of Flexible
Image Transport Standard (FITS) files. The MLA has two operational
modes: "standby" and "science". Within the MLA's science mode are three
commandable detector threshold modes, five range window modes, and two
detector gain modes. In addition to measuring the range to the surface,
the MLA also measures the surface reflectance properties at the laser
wavelength for nadir geometries (radiometry measurements). The MLA EDRs
consist of a table that includes range and radiometry information for
each laser return pulse. Each measurement consists of the round-trip
time-of-flight in milliseconds, the outgoing and return energy in mJ of
each pulse, the threshold setting of the detector, and other
measurement-related parameters.

*RS*

The RS investigation uses the spacecraft coherent X-band telemetry
system to obtain range-rate (or Doppler) and range measurements. The
former is the radial velocity component of the spacecraft relative to
the ground station, and the latter is the distance between the two.
Analysis of these data sets yields solutions for the spacecraft orbit
relative to the planetary center of mass, after account is taken of
propagation effects (through the interplanetary medium and the
atmosphere and ionosphere of Earth), the precise location of the ground
station, and the motions of the ground station relative to the solar
system barycenter due to Earth's orbital and rotational motions, among
other factors. More precise and accurate orbital solutions are obtained
when the radiometric Doppler and ranging data are combined with
additional measurements of the spacecraft position relative to the
planet, which for MESSENGER are the altimetric data from MLA. A combined
solution for the spacecraft orbit plus the planetary shape, gravity, and
rotation state will be obtained from the radiometric and altimetric
data.

**3.2.2 Calibrated Data Records**

CDRs are processed data derived from the EDRs consisting of decompressed
and radiometrically calibrated data. Data values are expressed in
physical units, such as radiance or reflectance. Ancillary data (CODMAC
Level 6), such as compression tables, calibration files, and viewing
geometry files (e.g., SPICE kernels), may be needed to construct CDRs.
In general, DDPs and DAPs are based on, but separate from, CDRs.
Ancillary data used in constructing the CDRs are archived to the PDS
commensurately with the CDRs. All CDRs are formatted to include standard
PDS labels. A brief description of each instrument's CDRs follows.
Detailed descriptions can be found in each instrument's SIS document.

*MDIS*

To convert MDIS EDRs to CDRs each image product is decompressed using
algorithms incorporating the appropriate compression tables and/or
compression algorithms. DN values are converted to radiance values using
calibration algorithms supplied by the Instrument Scientist based on
in-flight and on-ground instrument calibration measurements.

*GRS*

EDRs from the GRS are histograms of pulse height counts per channel. To
convert these EDRs to CDRs, any compression applied to the original
measurements prior to storage on the SSR and downlink via the DSN must
be removed. Each histogram is decompressed using decompression
algorithms incorporating the compression tables and/or compression
algorithms from their original construction. Event counts per channel
must be converted to a common energy scale so spectra can be summed
together. Corrections included are for energy gain, offset, integral
non-linearity (INL), and differential non-linearity (DNL). Summed
spectra can be analyzed to determine the peak areas of gamma-ray lines.
Normally, only the anticoincidence spectrum, which has the best
signal-to-noise ratio, will be analyzed for peak areas. The peak areas
can be converted to photon fluxes using calibration efficiencies, which
include both intrinsic detector efficiency and attenuation through the
material surrounding the detector. These efficiencies are derived from
both ground-based and in-flight measurements and calculations. The
efficiencies and the necessary algorithms to do the conversions are
supplied by the Instrument Scientist.

*NS*

EDRs from the NS are histograms of pulse height counts per channel. To
convert these EDRs to CDRs, any compression applied to the original
measurements prior to storage on the SSR and downlink via the DSN must
be removed. Each histogram is decompressed using decompression
algorithms incorporating the compression tables and/or compression
algorithms from their original construction. Event counts per channel
must be converted to a common energy scale so spectra can be summed
together. Corrections included are for energy gain, offset, INL, and
DNL. The count rates can be converted to neutron fluxes as a coarse
function of energy using background subtraction methods and calibration
efficiencies, which include both intrinsic detector efficiency and
attenuation through the material surrounding the detector. These
efficiencies are derived from both ground-based and in-flight
measurements and calculations. The efficiencies and the necessary
algorithms to do the conversions are supplied by the Instrument
Scientist.

*XRS*

EDRs from the XRS are histograms of event counts per channel. To convert
these EDRs to CDRs any compression applied to the original measurements
prior to storage on the SSR and downlink via the DSN must be removed.
Each histogram is decompressed using decompression algorithms
incorporating the compression tables and/or compression algorithms from
their original construction. Event counts per channel are converted to
energy spectra using calibration algorithms supplied by the Instrument
Scientist based on in-flight and on-ground instrument calibration
measurements. The peak areas can be converted to photon fluxes using
calibration efficiencies, which include both intrinsic detector
efficiency and attenuation through the material surrounding the
detector. These efficiencies are derived from both ground-based and
in-flight measurements and calculations. The efficiencies and the
algorithms to do the conversions are also supplied by the Instrument
Scientist.

*MASCS/VIRS*

All EDR spectra are a vector of values (spectral channels), where the
values correspond to data numbers (DNs). VIRS CDRs are produced by first
decompressing the EDRs using algorithms incorporating the appropriate
compression tables and/or compression algorithms. Raw spectra DNs are
converted to radiance values using calibration algorithms supplied by
the Instrument Scientist based on in-flight and on-ground instrument
calibration measurements. Radiance values are converted to reflectance
using a solar spectrum.

*MASCS/UVVS*

UVVS CDRs are produced by first decompressing the EDRs (event counts per
wavelength on a given PMT) using algorithms incorporating the
appropriate compression tables and/or compression algorithms. Counts per
wavelength are converted to Rayleighs using calibration algorithms
supplied by the Instrument Scientist based on in-flight and on-ground
instrument calibration measurements. Two distinct types of CDRs are
produced, one corresponding to atmosphere survey observations and the
second to atmosphere altitude profile observations.

*EPPS/EPS*

Calibrated EPS data are generated by reversing the log compression
algorithm for each of the rate data channels, converting particles per
accumulation period to particles per second, removing non-linearities
from the instrument response by performing a so-called "R versus R"
correction ("R" represents "rate"; note that the correction for any one
channel may involve the use of other channels that are adjacent in
energy), and finally converting the resulting linear rates (counts per
second) into differential intensities (particles / (cm^2^.s.sr.keV) with
the use of channel-specific multipliers that involve the so-called
geometric factors and channel-energy band passes. Because information
about the instrument calibration evolves rapidly, the Calibrated Data
Records will initially consist (early in the MESSENGER program) of data
channels represented as counts per second. The conversion to intensity
will be performed "on the fly" when requested by the user with software
developed for that purpose. Calibrated Data Records also consist of the
unpacked PHA data (originally 48-bit words). The unpacking processes
yields multiple words for each particle event representing detection
process (electron, low-energy ion, or high-energy ion process),
detector, energy, and time-of-flight. The energy and time-of-flight are
converted from PHA numbers to keV and nanoseconds, respectively.

*EPPS/FIPS*

Calibrated FIPS data are generated by reversing the log compression
algorithm for each of the rate data channels, converting particles per
accumulation period to particles per second, removing non-linearities
from the instrument response by performing a so-called "R versus R"
correction ("R" represents "rate"; note that the correction for any one
channel may involve the use of other channels that are adjacent in
energy), and finally converting the resulting linear rates (counts per
second) into differential intensities (particles / (cm^2^.s.sr.keV) with
the use of channel-specific multipliers that involve the so-called
geometric factors and channel-energy band passes. Because information
about the instrument calibration evolves rapidly, the Calibrated Data
Records will initially consist (early in the MESSENGER program) of data
channels represented as counts per second. The conversion to intensity
will be performed "on the fly" when requested by the user with software
developed for that purpose. Calibrated Data Records also consist of the
unpacked PHA data (originally 28-bit words). The unpacking process
yields multiple words for each particle event representing energy per
charge, time-of-flight, "x-position", and "y-position". The
time-of-flight, x-position, and y-position are converted from PHA
numbers to nanoseconds, centimeters, and centimeters, respectively.

*MAG*

To obtain CDRs the magnetic field XYZ readings in each of the MAG-EDR
types are uncompressed, if necessary, using the information in the EDR
headers. Counts, 0000~16~ to FFFF~16~, are converted to signed integers
and then multiplied by the pre-launch calibration matrix appropriate for
the full-scale magnetic magnitude value range indicated in the EDR
header. The matrix includes the scale factor conversion to nanoTesla
(nT) units and corrects for small non-orthogonality effects in the
sensor to yield orthogonal XYZ magnetic field values in sensor
coordinates. This matrix and its inverse are included in Ancillary Data.
The header time tag is used to evaluate the time of each magnetic field
reading to 0.05-s resolution using the packet time tag and sample rate.
No other time corrections are applied (e.g., for instrument latency).
Time is expressed in spacecraft event time, e.g. Mission Elapsed Time
(MET), or equivalent. Three MAG-CDRs are produced, MAG-LHK3, MAG-SSD3
and MAG-BST3 records, which map one-to-one to their corresponding EDRs.
Each record consists of a series of time-tagged vector magnetic field
values, up to 10 in each LHK3 record, up to 200 in each SSD3 record, and
640 in each BST3 record.

Two types of intermediate, CODMAC Level-4, records are produced. The
first type are assembled time series created by combining all CODMAC
Level-3 records starting in a given day to produce one CODMAC Level-4
record per day. All LHK3 records starting on a given day are combined to
produce one LHK4 record. Similarly, all SSD3 records starting in a given
day are combined to produce one SSD4 record. The BST3 records are
combined in a different way. Each set of 15 BST3 records corresponding
to a given burst interval is combined into a single BST4 record so that
there is one BST4 record for every burst interval. There may be none or
more than one BST4 records for a given day. BST4 records are not divided
by day boundaries, that is, all BST3 records for a given burst interval
are included in a single BST4 even if a day boundary occurs during the
burst interval. In addition to combining records into single daily or
burst files, any spacecraft magnetic fields derived by post-launch
analysis are subtracted from the magnetic field values in all three
types of records, LHK4, SSD4 and BST4. Spacecraft magnetic field
corrections will be provided as Ancillary Data. The second type of
CODMAC Level-4 products are summary electronic-format survey plots of
the time series in LHK4, SSD4, and BST4 records.

*MLA*

The MLA EDRs are records of times of flight measured versus mission
elapsed time. The CDRs are derived from the MLA EDRs by applying
decompression (where applicable) and calibration algorithms supplied by
the Instrument Scientist. The calibration involves converting the range
measurement to meters and making corrections for pulsewidth, pulse
energy, and their sensitivity to temperature and other instrument and
planetary parameters.

*RS*

The RS EDRs contain two data types: the Doppler shift in Hz versus UTC
(universal time) and the Earth-to-spacecraft range versus UTC. CDRs are
derived from the RS EDRs by applying decompression (where applicable)
and calibration algorithms supplied by the Instrument Scientist. The
Doppler shift is measured using the spacecraft coherent transponder,
which is phase-locked to the radio signal as received from the Earth.
The Doppler shift is used to obtain the range-rate or radial velocity
component. The calibration involves converting the Doppler measurements
to engineering units by making corrections for atmospheric and
interplanetary propagation effects, station location, and other factors.
The range measurement uses the ranging transponder to measure the round
trip time-of-flight for a radio signal between the spacecraft and the
Earth. Calibration involves corrections for propagation effects, station
location, and additional factors.

**3.2.3 Derived Data Products**

Table 3 lists the derived data products (DDPs) that the MESSENGER
project will deliver to the PDS. These DDPs are outlined in the
MESSENGER CSR. A brief description of each instrument's DDPs follows.
Detailed descriptions can be found in each instrument's SIS document.
The ancillary data (Level 6) needed to produce these products are
described elsewhere in this section and in section 3.3. It is the
responsibility of the Science Team to produce these products and deliver
them to the MESSENGER SOC.

*MDIS*

The DDP for the MDIS cameras are a monochrome and multispectral image
catalogue that describes the geometry and camera setting of each MDIS
observation. This database will aid users not familiar with the mission
to find observations rapidly to meet their scientific goals and is an
important value-added product for the entire mission. This catalogue is
separate from the EDR and CDR images, and can serve as an observation
search tool.

*GRS*

The DDPs are the elemental compositions derived from the incident photon
flux on the detector for each gamma-ray peak. The conversion from photon
flux to composition depends on an assumed model composition that in turn
is used to derive the neutron leakage fluxes and gamma-ray fluxes. A
neutron-photon Monte Carlo code, such as the MCNPX code that is being
used by Mars Odyssey (Boynton et al. 2002), calculates the fluxes from
the assumed composition. These calculated values are compared with the
measured values, and appropriate changes are made to the model and new
calculations are made until there is agreement between the two.

*NS*

Neutron spectra do not have sharp peaks corresponding to energies
associated with individual elements but have higher count rates. Use of
sophisticated spectral background subtraction algorithms and the
"ram/wake" detector concept, along with filter functions derived from
neutron transport computations (using codes such as MCNP, Feldman et al.
1995) that improve energy definition for thermal and epithermal
neutrons, allow identification of very light elements such as hydrogen
and coarse determination of average atomic mass.

*XRS*

The DDPs are the elemental composition ratios derived from the incident
photon flux on the detectors for each X-ray peak in the three
planet-looking detectors. Fitting of the three spectra is done
simultaneously to develop a self-consistent result. The conversion from
photon flux to composition ratios depends on the input solar spectrum
derived from the solar monitor. The shape of this spectrum is compared
to solar models to determine a solar temperature. The solar temperature
is applied to the fitted results from the planet-looking detectors as an
energy-dependent normalization.

*MASCS/VIRS*

VIRS DDPs listed in the MESSENGER CSR are defined as surface radiance
spectra. These can be described as a table of validated, interpretable,
reducible radiance spectra at given latitudes, longitudes, footprint
dimensions and orientations, time markers, and viewing geometries for
the entire planet (and a solar reference spectrum). The data set will be
a set of data cubes or tables which can be combined to make a "global
spectral dataset".

*MASCS/UVVS*

UVVS DDPs will be tables of atmospheric emission radiance profiles
("limb tangent height spectra") of Mercury as a function of altitude
from the surface, location of profile, viewing geometry, time of Mercury
day and year, and possibly solar distance and Mercury radial velocity.
UVVS spectra have discrete emission lines that identify individual
elements.

*EPPS/EPS*

EPS begins with a 3-dimensional data cube that has the data parsed
according to energy, species (electrons and ion mass composition), and
angle (look directions). Higher-level data products are derived by (1)
converting the angular directional information into geophysically
significant coordinates, and (2) reducing the dimensionality of the
information by performing various cuts through and summations over
portions of the data cube, and performing various weighted integrations
over selected regions of the data cube (thereby obtaining "moments").
Derived data products defined to date include: (1) "energy spectra" of
various selected species; (2) such distribution "moments" as pressure,
density, integral intensity, and integral energy intensity for various
selected species; (3) ion mass species distributions over selected
ranges of energies, and (4) pitch angle distributions for various
species and over selected ranges of energies (pitch angle is the angle
with respect to the local magnetic field direction). Generally, derived
data products are generated "on the fly" when requested by the user by
software developed for that purpose. They are not generated as a matter
of course for all of the data.

*EPPS/FIPS*

FIPS begins with a 4-dimensional data cube that has the data parsed
according to energy/charge, mass/charge, and two different angles (look
directions). Higher-level data products are derived by (1) converting
the angular directional information into geophysically significant
coordinates, and (2) reducing the dimensionality of the information by
performing various cuts through, and summation over portions of, the
data cube, and performing various weighted integrations over selected
regions of the data cube (thereby obtaining "moments"). Derived data
products defined to date include: (1) mass per charge distributions over
selected ranges of energy/charge, (2) "energy spectra" of various
selected species; (3) such distribution "moments" as pressure, density,
integral intensity, and integral energy intensity for various selected
species; (4) pitch angle distributions for various species and over
selected ranges of energies; and (5) angle-space images of particle
arrival directions (for various mass species and over various ranges of
energy/charge) oriented with respect to, and in some cases remapped to,
one or more geophysically significant coordinate systems derived with
knowledge of the solar wind direction, the local magnetic field
direction, and the direction to Mercury.

*MAG*

The MAG-DDRs consist of vector magnetic field values in physical
coordinates together with absolute time (e.g., UTC) and spacecraft
position in physical coordinates. The conversion of the vector magnetic
field values to physical coordinates includes transformation from MAG
sensor coordinates to spacecraft coordinates defined by the attitude
sensors (star cameras) in the spacecraft avionics. Transformation to
physical coordinates from spacecraft coordinates is performed using
SPICE routines, as is evaluation of spacecraft position. Different sets
of values corresponding to multiple coordinate systems will be provided:
inertial celestial (e.g., J2000), Mercury-centered body-fixed,
Mercury-centered magnetospheric, Mercury-centered solar wind, and solar
orbital (appropriate for cruise). Detailed definitions of some of these
coordinate systems remain to be formulated. Magnetospheric coordinates
in particular depend on the orientation of Mercury's magnetic dipole as
derived under derived analysis products and will therefore be updated
during the mission.

*MLA*

The MLA DDPs include range profiles and radiometry. Range profiles are
the time series of measured ranges. There are two methods for deriving
range values. The MLA receiver has three channels with different time
constants (10 ns, 60 ns and 270 ns). In the narrowest filter channel
there are two threshold levels. The receiver records 4 stops (leading
and trailing) if a return pulse triggers this channel. From these
values, the range is found by centroiding, and the return energy is
found by fitting to a pulse shape. These are the MOLA-type range
measurement and the radiometry measurement. The other channels have
different, lower threshold values, and the receiver will record up to 10
stops from each of them. Over some window the receiver constructs a
histogram from which it picks out the range. This is the second method
for determining the range value. Given an orbit solution, planetary
shape and rotation solution and pointing information, these can be
converted to ranges along a latitude-longitude track. The orbit, shape,
rotation, and gravity are all solved simultaneously from the set of
range profiles. Radiometry is the surface reflectance measurement at
zero phase.

*RS*

The RS DDPs include the Doppler range-rate data, the ranging data, and
radio occultation data (time intervals when signal is lost because the
spacecraft passes behind the planet as seen from Earth). These are
expressed in engineering units, after calibrations, corrections,
resampling, and weighting of data.

**3.2.4 Derived Analysis Products**

Table 4 lists the derived analysis products (DAPs) that the MESSENGER
project will deliver to the PDS. These DAPs are outlined in the
MESSENGER CSR. A brief description of each instrument's DAPs follows.
Detailed descriptions can be found in each instrument's SIS document.
The ancillary data (Level 6) needed to produce these products are
described elsewhere in this section and in section 3.3. It is the
responsibility of the Science Team to produce these products and deliver
them to the MESSENGER SOC.

*MDIS*

Derived analysis products from the MDIS fall into two broad categories,
those produced from images acquired during the flybys and those from the
orbital operations. From the flybys products include four quadrature
monochrome mosaics (NA camera) with a central resolution of \~1 km/pixel
(resolution falls off radially towards the limb), four quadrature
7-color mosaics with a central resolution of \~5 km/pixel, and two
3-color approach and departure movies. During orbital operations
systematic mapping will result in a global monochrome basemap at 250
m/pixel, a merged flyby and orbital global color mosaic in seven
spectral filters at \~1 km/pixel, local stereo-based digital elevation
models, and very-high-resolution (NA camera) local strip mosaics in the
northern hemisphere (best resolutions will be on the order of 20
m/pixel).

*GRS*

Identification of elements and their concentrations covering a wide
range of spatial scales are the first-order DAPs. Other products result
from gamma-ray spectra that can be summed spatially in many different
ways including accumulations over latitude-longitude bins, accumulations
over spatial features on the surface, and spatial accumulations over
time to map temporal changes. Each of these accumulations can be
converted to composition, and then these compositions can be mapped onto
the planet with the spatial resolution inherent with the GRS
(approximately equal to the altitude).

*NS*

Identification of hydrogen and its concentration and average atomic mass
covering a wide range of spatial scales are the first-order DAPs. Other
products result from neutron spectra that can be summed spatially in
many different waysincluding accumulations over latitude-longitude bins,
accumulations over spatial features on the surface, and spatial
accumulations over time to map temporal changes. Each of these
accumulations can be converted to coarse "elemental composition", and
then these "elemental compositions" can be mapped onto the planet with
the spatial resolution inherent with the NS (approximately equal to the
altitude).

*XRS*

The primary derived analysis products are element identification and
composition ratios over as much of the planet's surface as possible. The
spatial resolution of composition maps will vary with the element and
counting statistics. Maps as a function of latitude and longitude will
be generated where feasible. Compositions of particular regions of
interest may also be possible.

*MASCS/VIRS*

Identification of minerals and their abundances globally, regionally,
and at specific locations are the first-order DAPs. Fe-bearing minerals
and Ca silicates can be identified through absorption band
characterization, TiO~2~ from short-wavelength characteristics, and FeO
through spectral uniformity. These and other products result from
ratioing different spectral channels, tangent finding for slopes, and
curve fitting for band parameters. Spatial coverage and resolution will
depend on altitude and orbit. The delivered DAP will include
interpolated maps of key wavelengths, ratios, and/or spectral absorption
band parameters.

*MASCS/UVVS*

Emission line strengths determine the elemental line-of-sight column
abundance of known (H, O, Na, K, Ca) and predicted (S, Si, Mg, Al, OH,
Fe, Al) atmospheric constituents. MASCS UVVS is very much a discovery
instrument, so specific DAPs will depend on what is actually detected.
Possible DAPs include a general Mercury exosphere model and
identification of volatile species and sources (with geographical,
altitudinal, and temporal dependences).

*EPPS/EPS*

EPS derived analysis products are products that involve multiple data
sets (for instance EPS+FIPS+MAG) and/or that require hands-on,
event-by-event analysis of the data. New derived analysis products will
be produced as the analysis of the data proceeds. Among those DAPs
defined to date are: (1) plasma beta parameter involving EPS and FIPS
moments with normalization by magnetic field pressure values; (2) other
plasma moments that involve combining the weighted integral moments
performed using EPS and FIPS data; (3) analytic functional spectral fits
that combine many data channels in a procedure that allows for improved
discrimination of different mass species and improved spectral
characterization over a broader range of energies; (4) phase space
densities of charged particles, where the conversion from intensity to
phase space densities involves the use of Mercury magnetic field models
derived with the help of the MAG sensor; (5) tables and statistical maps
of magnetospheric regions that includelocations of various
magnetospheric boundaries, locations of regions of magnetic connectivity
to Mercury; spatial distributions of various hot plasma moments,spatial
distributions hot plasma composition, and regions of bursts and other
dynamical activity.

*EPPS/FIPS*

FIPS derived analysis products are products that involve multiple data
sets (for instance FIPS+EPS+MAG) and/or that require hands-on,
event-by-event analysis of the data. New derived analysis products will
be produced as the analysis of the data proceeds. Among those DAPs
defined to date are: (1) plasma beta parameter involving FIPS and EPS
moments with normalization by magnetic field pressure values; (2) other
plasma moments that involve combining the weighted integral moments
performed using FIPS and EPS data; (3) analytic functional spectral fits
that combine together many data channels in a procedure that allows for
improved discrimination of different mass species and improved spectral
characterization over a broader range of energies; (4) phase space
densities of charged particles, where the conversion from intensity to
phase space densities involves the use of Mercury magnetic field models
derived with the help of the MAG sensor; (5) two-dimensional particle
images with overlaying predictions of particle arrival directions based
on the pick-up and other processes; (6) tables and statistical maps of
magnetospheric regions that include locations of various magnetospheric
boundaries, spatial distributions of various cold and hot plasma
moments, spatial distributions of plasma composition, and regions of
bursts and other dynamical activity.

*MAG*

MAG derived analysis products are produced in two basic areas: planetary
magnetic field and magnetosphere. The planetary magnetic field MAG-DAPs
will consist of a dipole model , a multipole model, and a
longitude/latitude map of departures from the model field over latitudes
northward of approximately 45°N.

The dipole representation of Mercury's magnetic field will include
magnitude and orientation and will initially assume a planet-centered
position. The dipole representation will be constructed from magnetic
field observations obtained within the Mercury magnetosphere and will be
updated approximately monthly as more data are acquired. The dipole
model will include an eccentricity when the uncertainty in the offset
dipole is less than approximately 0.1 planetary radii, estimated to be
possible approximately three months after orbit insertion. The dipole
model will be used to organize magnetospheric observations in magnetic
coordinates.

In addition to the dipole model, a multipole model, including terms at
least through the quadrupole moment, will be constructed after three
months of data have been obtained and repeated approximately every three
months. A fit including octopole terms will also be attempted. The
multipole representation will be constructed from magnetic field
observations obtained within the Mercury magnetosphere corrected for
contributions of the magnetospheric current systems. Restriction of data
to particularly quiet passes may be required. The reliability of higher
order terms will depend on the accuracy of the Mercury magnetosphere
model. Present estimates indicate that perhaps meaningful quadrupole
terms may be obtained but that octopole terms are likely to have large
uncertainties.

In the northern hemisphere data will be obtained at altitudes down to
200 km. These data provide an opportunity to specify the level of
higher-order structure in the magnetic field in this region. Six months
into the orbital phase of the mission, the departure of measurements
(with the external field removed) from the dipole field model will be
computed in body-fixed coordinates. A map of these residuals will be
constructed by averaging the residuals over bins approximately 6° in
latitude bins by \~100 to 200 km in longitude. We expect the map to
cover latitudes northward of approximately 45°N.

MAG-DAPs of primary relevance to magnetospheric studies will consist of
magnetopause and shock-crossing identifications and residual magnetic
fields after removal of the planetary magnetic field. EPPS data will be
used to confirm the crossings identified in the magnetic field data. The
residual magnetic fields will be used to develop a semi-empirical
magnetospheric model. As this model is refined it will be used to
improve the corrections applied in analysis of the intrinsic magnetic
field. Burst observations will be processed for spectral signatures of
heavy ions and wave and turbulence processes in various areas of the
magnetosphere. Analysis of these data will be event-,driven and will be
performed in close association with EPPS observations as will analysis
of highly time-dependent signatures in the magnetic field. The results
of these analyses will be incorporated in the development of a Mercury
magnetospheric model.

*MLA*

The DAPs produced from the MLA observations include northern hemisphere
topographic profiles and map, altimetric profiles, a determination of
the libration amplitude, and a measure of the right ascension (RA) and
declination (DEC) of Mercury\'s rotational pole. All of these DAPs fall
out of the simultaneous solution for orbit, shape, rotation, and
gravity. The primary data product will be a record of the altimetry
measurement presented as a measurement of the radius of the planet at a
specified location (latitude and longitude). This will be generally
known as the altimeter profile product. The altimeter profile product
will have an along-track resolution of 0.8-1 km. This product is
developed by first determining the position of the spacecraft from the
tracking data, using the spacecraft quaternion information to derive the
location of the laser spot on the surface of the planet, and then
deriving the radius of the planet at the spot location from a knowledge
of the radius to the satellite and the altimeter range measurement to
the surface. The radius measurements will be reduced to topography
(elevation referenced to a geoid) versus latitude and longitude in the
Northern hemisphere. A gridded topography map of the northern hemisphere
will also be produced from the altimeter profiles. The libration
amplitude and phase is determined from a combination of the altimetry
data and the tracking data, to find the lowest order longitudinal
harmonics (through order 4) referenced to the planetary center of mass.
Both datasets can independently provide a measure of the libration, and
the tracking data provide the measurement of the obliquity, but a
simultaneous solution from both the tracking and the altimetry provides
the strongest solution for all parameters.

*RS*

The RS DAPs include a northern hemisphere gravity model and spherical
harmonic models of the gravity field and global shape. In addition,
occultation radii are determined at specific latitudes and longitudes.
The gravity and shape are determined from a combined solution for the
spacecraft orbit and the planetary shape, gravity, and rotation state,
as mentioned above. A spherical harmonic gravity model to degree and
order 16 will be recovered, with a resolution of about 400 km in the
northern hemisphere and about 1500 km in the southern hemisphere. A
spherical harmonic shape model, likewise to degree and order 16, will be
determined from the gravity and MLA altimetry data. The times of loss
and acquisition of radio signals in the occultation data will be reduced
to occultation radii versus latitude and longitude, using the spacecraft
orbit, the planetary rotation state, and knowledge of the Earth viewing
geometry.

**3.3 Ancillary Data**

Level 6 ancillary data include data needed to produce the MESSENGER
science products, such as calibration and compression algorithms and
tables, as well as engineering products.

**3.3.1 Calibration Data**

Each instrument will be obtaining pre-flight and in-flight calibration
measurements. These calibration measurements will characterize the
performance and capabilities of each instrument and will be used to
derive the calibration algorithms and tables needed to interpret the
scientific measurements made during the mission. Details of the
calibration data expected from each instrument, in addition to
calibration data archive guidelines, can be found in their individual
Calibration Plans. The schedule for archive delivery of calibration data
is described in section 6 of this document.

**3.3.2 Navigation Data**

Engineering data, while not strictly science data, can be used to aid
the interpretation and processing of science data and as such will be
archived as Level 6 ancillary data. Some engineering products,
predominately SPICE files, are necessary for producing the higher-level
science products, such as the DDPs and DAPs.

SPICE is an acronym used to describe a suite of elemental ancillary data
sets, often called kernels:

> S Spacecraft ephemeris, with files containing spacecraft location as a
> function of time
>
> P Planetary/satellite ephemerides and associated target-body physical
> and cartographic constants
>
> I Instrument information, including mounting alignment and
> field-of-view size/shape/orientation
>
> C Camera orientation of a spacecraft\'s primary coordinate systems and
> possibly angular rates
>
> E Event information, including nominal sequences, real-time
> commanding, unscheduled events, and experimenter's notebook comments.

Flight operations teams will generate most SPICE kernels with some
instrument information and sequence data obtained from instrument teams.
Where appropriate, there will be both predicted and reconstructed SPICE
files. Reconstructed SPICE kernels will typically be generated within 3
weeks of data acquisition and made available to instrument teams. SPICE
kernels will be used together with a toolkit of software modules (to be
supplied through the PDS by JPL's Navigation and Ancillary Information
Facility) at investigator institutions to generate the derived ancillary
data needed to help plan observations and to process the returned data.
Table 5 summarizes the SPICE data expected for this mission.

Table 5. SPICE Data Summary

  -------------------------------- ---------------- ------------------------
  **Data File**                    **Originator**   **Type of Information**

  Planetary ephemeris              NAIF             Planetary position vs.
                                                    time

  MOC S/C ephemeris -- short term  NAV              Predicted S/C position
  predicts                                          vs. time

  MD S/C ephemeris -- long term    NAV/MD           Predicted S/C position
  predicts                                          vs. time

  SOC S/C ephemeris - actual       NAV              S/C position vs. time

  S/C attitude -- short term       MOC - Statesim   Predicted S/C
  predicts                                          quaternians

  S/C attitude -- long term        SOC              Predicted S/C
  predicts                                          quaternians

  Instrument pointing              SOC w/ NAIF      MDIS boresight pointing
                                   support          

  Instrument field of view         SOC w/ NAIF      MDIS FOV definitions
                                   support          

  Frame kernels                    SOC w/ NAIF      MDIS frame definitions
                                   support          

  MET/UTC correlation: coarse      MOC              MET to UTC conversion

  MET/UTC correlation: fine        MOC              MET to UTC conversion
  -------------------------------- ---------------- ------------------------

**3.3.3 Engineering Products**

Engineering products are a subset of Ancillary Products used in the
interpretation of instrument data. They may include such information as
instrument voltages, currents, and temperatures. The spacecraft health
status may also be included as an engineering product.

**3.4 Documentation**

Documentation of data acquisition and processing histories is crucial to
successful long-term use of project data and will contain information
delineating why data sets were acquired, including whether they were
part of a coordinated sequence. Information on spacecraft events that
affected the sequences and data products will also be included. The
actual (as opposed to predicted) SPICE files will be transferred to a
long-term archive along with raw and reduced data.

Information needed to understand fully EDRs, SPICE files, and reduced
data will also be generated for long-term use of MESSENGER project data.
Documents, their providers, and due dates will include:

-   For each instrument, a calibration requirements document (Instrument
    Scientists, Jan. 2003)

-   Instrument description and pre-launch calibration reports (Lead
    Engineers and Instrument Scientists, launch + 30 days)

-   In-flight calibration reports (Instrument Scientists and Lead
    Engineers, as appropriate)

-   Descriptions of data products from particular instruments and how
    they were generated (such as contained in the instrument SIS
    documents)

-   Instrument-specific sequence of events (SOC, maintained
    continuously)

Documentation to be provided by the project will include a Mission
Operations Report, stipulating how the mission plan was actually carried
out.

**3.5 Software**

It is expected that standard data products delivered by the PI or
science team should be in a format that is accessible by other users. If
the products cannot be accessed using commonly available software tools,
then the products should be accompanied by software, detailed
algorithms, or descriptions that allow a user to access the data.

**4. Roles and Responsibilities**

This section summarizes the roles and responsibilities of the
organizations (and the key personnel within these organizations) who are
involved in the generation, validation, transfer, and dissemination of
MESSENGER data to both the scientific community and the general public.
These organizations include the MESSENGER project, the PDS, The Johns
Hopkins University Applied Physics Laboratory (JHU/APL), the Carnegie
Institution of Washington (CIW), and Applied Coherent Technologies
(ACT). The MESSENGER project, through its Science Team and SOC, is
responsible for archive generation and validation. The PDS is
responsible for ensuring that the archive meets PDS standards (including
peer review of the data), advising the MESSENGER project and its Science
Team on archive-related issues, maintaining active archives of MESSENGER
products for access by the science community, and interfacing with the
National Space Science Data Center (NSSDC) for long-term archiving of
the MESSENGER data. Table 6 summarizes the responsibilities for
producing and archiving the standard products, ancillary data, and
documentation.

**Table 6. Product responsibility**

  -------------------------------------- ----------- -------------- -----------------
  **Product**                            **Level**   **Producer**   **Mission Source
                                                                    to PDS**

  Raw instrument telemetry               1           MOC            SOC

  Cleaned & merged instrument telemetry  1           MOC            SOC

  **STANDARD PRODUCTS**                                             

  Individual instrument EDRs             2           SOC            SOC

  Individual instrument CDRs             3           SOC            SOC

  Catalogued images                      3,4         GG             SOC

  γ-ray spectra, neutron flux            3,4         GC             SOC

  B-field vectors                        3,4         AM             SOC

  Range profiles, radiometry             3,4         GP             SOC

  Limb tangent height spectra            3,4         AM             SOC

  Surface reflectance spectra            3,4         GC             SOC

  Particle energy vs. composition vs.    3,4         AM             SOC
  angle distributions                                               

  X-ray spectra                          3,4         GC             SOC

  Doppler data, ranging data,            3,4         GP             SOC
  occultation times                                                 

  Global element map                     5           GC             SOC

  Spectral unit map                      5           GC             SOC

  Global monochrome map                  5           GG             SOC

  Stereo maps                            5           GG             SOC

  Multispectral image catalogue          5           GG             SOC

  North-hemisphere topography map        5           GP             SOC

  Altimetric profiles                    5           GP             SOC

  North-hemisphere gravity model         5           GP             SOC

  Multipole internal magnetic field      5           AM             SOC
  model                                                             

  Time-dependent magnetosphere model     5           AM             SOC

  Libration amplitude                    5           GP             SOC

  RA and DEC of Mercury's rotational     5           GP             SOC
  pole                                                              

  Spherical harmonic gravity field       5           GP             SOC

  Low-degree global shape                5           GP             SOC

  North-hemisphere topographic profiles  5           GP             SOC

  Exosphere model                        5           AM             SOC

  Volatile species and sources           5           AM             SOC

  **ANCILLARY DATA**                                                

  SPICE                                  6           See Table 5,   SOC
                                                     Originator     

  Command history                        6           MOC            SOC

  Calibration files, tables, algorithms  6           ST             SOC

  Compression files, tables, algorithms  6           ST, MOC        SOC

  **DOCUMENTATION**                                                 

  Calibration Description Papers         N/A         ST             SOC

  Instrument Description Papers          N/A         ST             SOC

  Data Product Descriptions              N/A         ST             SOC

  Instrument-specific sequence of events N/A         SOC            SOC
  -------------------------------------- ----------- -------------- -----------------

\* GG: Geology Group, GC: Geochemistry Group, GP: Geophysics Group, AM:
Atmosphere and Magnetosphere Group, ST: Science Team, SOC: Science
Operations Center, MOC: Mission Operations Center.

**4.1 MESSENGER Project**

The MESSENGER project is responsible for the production and delivery to
PDS of documented archives of raw and reduced data records (EDRs and
RDRs) that meet PDS standards and for release of data to the general
public. The key personnel and sub-groups within the MESSENGER project
involved with the production and delivery of archived data include the
Principal Investigator (PI), the Project Scientist (PS), the Instrument
Scientists, the Science Team, the cognizant Co-Investigators (cognizant
Co-Is, who are also members of the Science Team), the SOC, and the Data
Archive Working Group (DAWG).

*Principal Investigator*

The MESSENGER PI is responsible for primary interactions with NASA
Headquarters, ensuring that Headquarters personnel are aware of
information releases before they occur, and for providing feedback from
Headquarters to other members of the MESSENGER project.  It is the
responsibility of the PI to formulate the policies and implementation
plans concerning the release of information and interactions with the
general public and the press.  It is the responsibility of the PI or his
designate to review all materials prior to release to the general public
and the press to insure compliance with NASA Headquarters and MESSENGER
project policies.

*Project Scientist*

The MESSENGER PS provides oversight to MESSENGER mission science
planning, data acquisition, data validation, and the generation and
validation of the data archives. Working with the PS (and his
designates) the science planning, data acquisition, data validation, and
data archive generation functions will be accomplished via the SOC, with
the assistance of the Science Team, the Instrument Scientists, and the
cognizant Co-Is.

The PS has primary responsibility for scientific oversight of routine
operations (such as science planning, data acquisition, and data
validation) and for ensuring that scientific findings are made available
to the media. Specifically, the PS or his/her designates, will:

-   lead preparation of the plan for data generation, archiving, and
    public release

-   ensure delivery of press release materials to NASA Headquarters that
    allow for sufficient lead time (typically one week)

-   coordinate preparation and Web release of summary and public
    relations data products by the Instrument Scientists (described
    below)

-   coordinate the preparation of audiovisual materials (press releases,
    interviews, press conference scripts, video file productions, etc.)
    with the APL media relations representative

-   identify themes or subjects for public release materials

-   enforce graphical standards for all publicly released data products.

*Instrument Scientists*

Each Instrument Scientist is a member of the SOC's Science Planning
Group (SPG) and is responsible for the daily planning of the data
acquisition that will enable the MESSENGER project to meet its science
objectives. Working with the tools provided by the SOC (and developed
with guidance from the Instrument Scientists), the Instrument Scientists
are responsible for data acquisition and data validation. In conjunction
with ACT, the prime MESSENGER project sub-contractor for the SOC, the
Instrument Scientist is responsible for providing calibration algorithms
for producing all CDRs. Instrument Scientists and cognizant Science Team
Co-Investigators are responsible for working with PDS and ACT personnel
on planning, generating, and validating archives from their instruments.

Each MESSENGER Instrument Scientist is responsible for following the
PI's policies and implementation plans concerning the release of
information and interactions with the public and press. He/she is also
responsible for providing the MESSENGER PI with information necessary to
support PI interactions with NASA Headquarters.

In summary, the Instrument Scientist will:

-   develop instrument performance and calibration requirements

-   lead the analysis of calibration data

-   develop data validation and calibration algorithms

-   apply the data validation and calibration algorithms to create the
    Level-2 or greater data given in Table 2, either (a) directly with
    delivery to the SOC of calibrated data that meet agreed-upon PDS
    standards, or (b) by supplying the SOC with agreed-upon algorithms
    to be applied in automated fashion in pipeline format

-   oversee the scientific validity of data products archived by the SOC

-   participate in and oversee the generation of flight instrument
    command sequences

-   provide science validation for the generated command sequences

-   generate for public release, via the Web, summary products showing
    the status of instrument data in a format appropriate to the
    instrument

-   generate for public release, via the Web, selected products suitable
    for reproduction in print and video forms, with separate captions
    written for general and technical audiences.

*Science Team*

The Science Team is organized into four broad disciplinary groups with
distinct but complementary interests. The Geology Group (interested in
the MDIS, MLA, and MASCS/VIRS observations), the Geochemistry Group
(interested in the GRNS, XRS, MDIS, and MASCS/VIRS observations), the
Geophysics Group (interested in the MLA, MAG, and RS observations), and
the Atmosphere and Magnetosphere Group (interested in the EPPS, MAG, and
MASCS/UVVS observations).

The Science Team, through its disciplinary groups, has the overall
responsibility for setting observing priorities for the spacecraft
instruments in order to meet the science goals of the MESSENGER project.
The data from these observations constitute the raw science data, the
fundamental element of the archive. In addition, the Science Team is
responsible for generating all DDPs and DAPs (listed in Tables 3 and 4)
that will be archived to the PDS for dissemination to the science
community. The Science Team is also responsible for providing
observation quality assessment criteria to the SPG.

*Cognizant Co-Investigators*

Within the Science Team there are cognizant Co-Is who are associated
with each instrument on board the MESSENGER spacecraft. The cognizant
Co-Is will lead the Science Team effort for producing these data
products and as members of the MESSENGER SOC are responsible for
delivery of these products from the Science Team to the MESSENGER SOC.
The cognizant Co-Is are responsible for clearing all liens generated by
the PDS review process on products produced by the Science Team groups
interested in their instrument's data set.

Cognizant Co-Is, as members of both the Science Team and the SOC, are
responsible for delivering to the SOC from the Science Team the RDRs
produced by the MESSENGER project. They are responsible for:

-   review of instrument performance and calibration requirements

-   participation in analysis of calibration data

-   review of data validation and calibration algorithms and their
    application

-   coordination of the generation of higher-order (CODMAC Level-3 and
    higher) data products given in Tables 3 and 4, and coordination of
    their delivery to the SOC in agreed-upon formats that meet PDS
    standards

-   review and participation in the generation of flight instrument
    command sequences

-   science validation for the generated command sequences

-   clearing all liens generated by the PDS review process on products
    produced by the Science Team groups interested in their instrument's
    data set.

**Figure 2. SOC organizational chart.**

**Figure 3. MESSENGER data flow**

*Science Operations Center*

The MESSENGER SOC is the center of activity for science planning, data
acquisition and analysis, and data archiving. The MESSENGER SOC,
physically located at JHU/APL, is operated under the direction of its
Lead Engineer who reports directly to the MESSENGER Project Manager. The
Project Scientist provides guidance and requirements to the SOC Lead
Engineer regarding the SOC's science requirements. Figure 2 shows how
the SOC fits within the MESSENGER Project's organizational structure.
The SOC supports and works with the Mission Operations Center (MOC), the
Science Team, cognizant Co-Is, Instrument Scientists, and the PDS in
order to fulfill its responsibilities. Figure 3 shows the informational
flow between the SOC (and its subdivisions) with the MOC, Science Team,
and PDS.

The SOC responsibilities can be divided into two categories: (1) those
involved with science planning, data acquisition, instrument operations,
and monitoring the science objective status, and (2) data dissemination
to the MESSENGER Science Team, data analysis and product generation, and
data archiving. The first category, referred to as "Science
Acquisition", is led by JHU/APL by the Project Scientist and includes
participation by the Science Team, cognizant Co-Is, Instrument
Scientists, and Instrument Engineers. The second category, referred to
as "Data Management and Archiving", is led by ACT and also includes
participation by the Science Team, cognizant Co-Is, Instrument
Scientists, and Instrument Engineers. Oversight of the SOC's science
acquisition and data processing is by the Project Scientist.

Under Science Acquisition the SOC will be responsible for:

-   Observation Planning

-   Observation Commanding

-   Validation

-   Science Objective Assessment.

Observation Planning involves the planning and generation of instrument
and spacecraft commands for science data acquisition. It is based on
inputs from Instrument Scientists, Instrument Engineers, and the
Navigation Team and spacecraft constraints from the MOC. Observation
Planning is the responsibility of the Science Planning Group (SPG), a
part of the SOC. Observation Commanding involves the development of
instrument commands and the translation of the observation plan into
command sequences for upload to the spacecraft through the MOC.
Observation Commanding is also a responsibility of the SPG. Validation
includes Observation Validation and Observation Quality assessment. The
first validates the executed command sequences and reschedules any
failed sequences necessary to fulfill the science objectives.
Observation Quality is an assessment of usability of the measurements
for achieving the science objectives. The assessment criteria are
supplied by the Science Team to the SPG.Validation is the responsibility
of the SPG. Science Objective Assessment includes the monitoring of data
coverage and mission status. Science Objective Assessment is the
responsibility of the SPG, who reports their assessment to the Science
Steering Committee. The SPG fulfills its responsibilities using tools
provided by the SOC. A detailed description of the SPG is provided in
the Science Planning Group Charter, and a summary is given below.

Under Data Management and Archiving the SOC will be responsible for:

-   Operations Support (both pre-flight and in-flight)

-   PDS-Compliant Archive Generation

Pre-flight Operations Support provides data ingestion capabilities,
product generation capabilities, and data access during instrument
calibrations and instrument integration and test. In-flight Operations
Support provides data ingestion capabilities, product generation
capabilities, data access, and data monitoring (such as coverage,
quality evaluation, and sensor performance) during the post-launch phase
of the mission. Operations Support ensures access to the data and
products by project personnel, particularly the Science Team. It also
involves the generation of a predefined set of data products, such as
SPICE files, in a timely manner. PDS-Compliant Archive Generation
includes the generation, validation, and delivery of the MESSENGER
archive data set. The generation of the data archive is the
responsibility of the Science Team with assistance by the SOC. The SOC
is responsible for preparing the instrument SIS documents that describe
the archive structure and data generated and produced from each
instrument's observations. The SOC supports the archive validation by
clearing all liens generated by the review process on products generated
by the SOC. The SOC is responsible for delivering the data archive on
the schedule described in Section 6 (Policies for Release of Data and
Public Information) of this document.

The SOC responsibilities outlined above flow into a set of requirements
that are described in detail in the SOC Requirements Document and
discussed in the Science Planning Group Charter.

*Science Planning Group*

The SPG is a subdivision of the SOC and is primarily responsible for
fulfilling the Science Acquisition responsibilities of the SOC. A
detailed description of the SPG is contained in the Science Planning
Group Charter. Its responsibilities include:

-   Development of instrument observing plans

-   Generation of instrument commanding

-   Conversion of observing plans into instrument command sequences for
    execution

-   Validation of data

-   Monitoring of data coverage

-   Maintenance of an updated total mission observing plan

-   Monitoring science acquisition in terms of completing mission
    success criteria.

The SPG reports to the MESSENGER Science Steering Committee to keep the
MESSENGER project up to date on the overall status of meeting the
science objectives. The MESSENGER project has input into the daily
observation planning through feedback to the SPG by the Science Steering
Committee.

*Science Steering Committee*

The MESSENGER Concept Study Report defines the purpose of the Scientific
Steering Committee (SSC) as "..overseeing the entire MESSENGER mission
science implementation, from instrument development through the
interdisciplinary synthesis of all data sets. The members of the SSC
include the Principal Investigator (SSC Chair), the Project Scientist
and the Deputy Project Scientist, the Science Payload Manager, the
Program Manager, and the four Science Team discipline leads.

The SSC will meet monthly during the orbital mission and as needed
during cruise and flyby mission modes. The SSC will monitor the
instrument payload performance and status, the status and progress of
data product production, the status of scientific publications, the
status of data coverage, and the status of archiving the mission success
criteria, and they will make recommendations to the SPG as necessary on
the basis of these issues.

*Data Archive Working Group*

The MESSENGER DAWG consists of representatives of the MESSENGER project
and the PDS.  The goals of the DAWG are to plan and ensure that
PDS-compliant data archives are generated, validated, and delivered to
the PDS following the MESSENGER project Archive Generation, Validation,
and Distribution Plan (AGVDP).

The AGVDP will be generated by the DAWG. The purpose of the document is
to define the formats and supporting deliverables, along with the data
archives, that the MESSENGER project is responsible for delivering to
the PDS. The document also defines what the PDS is to expect from the
MESSENGER project, and what it will be responsible for making accessible
to the science community.

The AGVDP will describe the specific generation, validation, and
transfer through the SOC to PDS of the team's data products.  The plan
will specify the contents of archives, the personnel or organization
responsible for generating each archive, estimates of the amount of data
to be delivered, and a schedule for delivery.  Instrument Scientists
(see Table 1) will contribute instrument-specific sections of the
document.  The AGVDP will be based on the policies and procedures
specified in this document.  

**4.2 Planetary Data System**

The NASA PDS is an active archive that provides high-quality planetary
science data products to the science community (Arvidson et al., 1994;
McMahon, 1996). This system evolved in response to science community
requests for improved availability of planetary data from NASA projects
through increased scientific involvement and oversight. PDS provides
access to data archives for scientists, educators, and the public.

The first objective of the PDS is to publish and disseminate documented
data sets, which are of use in scientific analyses. Whereas the media of
the published data vary, all PDS-produced products are peer-reviewed by
scientists and data engineers to ensure that the data and the related
materials are appropriate and usable. PDS data sets are typically
published as archives, collections of peer-reviewed data along with
documentation, ancillary information (such as calibration data),
software, and any other tools needed to understand and use the data. PDS
provides access to data by a system of online and compact disc archives.

The PDS is the primary organization within NASA responsible for
archiving planetary data and is the primary mechanism through which the
MESSENGER project will disseminate its mission data to the science
community. The lead PDS node for interfacing with the MESSENGER mission
is the Geoscience (GS) node at Washington University. The lead node will
be supported by other PDS nodes such as the Imaging (I) node for
assistance in dealing with the MDIS observations, the Planetary Plasma
Interactions (PPI) node for assistance in dealing with the MAG and EPPS
observations, the Atmospheres (A) node for assistance in dealing with
the MASCS observations, the Radio Sciences (RS) node for assistance in
dealing with the RS observations, and the Navigation and Ancillary
Information (NAIF) node for assistance in dealing with the navigation
and engineering data.

The PDS Geosciences Node Manager, Raymond Arvidson, will work with the
MESSENGER SOC and DAWG to ensure that overall plans are in place and
that the MESSENGER project meets its archiving commitments.  A PDS
sub-node manager has been identified for each MESSENGER instrument (see
Table 1) to facilitate the implementation of the archive
plans.  Relevant PDS personnel will participate in archive planning
efforts for each instrument to ensure that: (a) archives are planned,
generated, and reviewed using PDS standards, (b) the archiving process
generates data products in pre-approved PDS standard formats, (c)
archives are constructed in ways that facilitate cross-mission and
cross-instrument data analyses, and (d) the PDS provides user services
that allow search and access to data in ways that transcend particular
instruments or data sets.  This participation will be coordinated by the
MESSENGER project's SOC and the MESSENGER DAWG.

The PDS is responsible for distributing the MESSENGER project archives
to the broad science community after the data have been released by the
project.  Distribution may be done electronically via the Internet or by
replication of archive volumes for delivery to users.  The PDS maintains
copies of project archives, and the relevant PDS discipline nodes are
available to provide information and expert assistance to users of the
data.

Specific functions of the PDS are to:

-   support the generation of the archive by advising the
    project/science teams on PDS archive standards, requirements, and
    documentation needs. PDS will also support the data validation
    activity to ensure that the formal peer review process, a
    requirement for data ingestion into PDS, proceeds with a minimum of
    problems

-   conduct a formal peer review of the archive, as mandated by PDS
    prior to acceptance of archive data

-   offer support to the MESSENGER Science Team and SOC in the
    resolution of liens that arise in the course of the peer review

-   produce archive volumes for distribution to the NASA-supported
    science community

-   provide the data archive volumes to NSSDC.

NSSDC is responsible for long-term preservation of the MESSENGER data
archive and for filling large data orders to the science community per
the Memorandum of Understanding, dated January 13, 1994, between the PDS
and NSSDC.

**4.3 The Johns Hopkins University Applied Physics Laboratory**

The JHU/APL will physically house the MESSENGER SOC. The Project
Scientist will coordinate the SOC science acquisition responsibilities,
with participation from the Science Team, cognizant Co-Is, Instrument
Scientists, and Instrument Engineers.

The JHU/APL Media Relations Office will be the prime point of contact
with the public and the media for engineering activities focused at APL.
The overall objective of the Media Relations Office is to maximize the
positive impact of information releases from the project. This office
will:

-   organize and implement press releases and/or press conferences

-   facilitate release of data and information meant for consumption by
    the press and public, including video feeds of interviews

-   review for aesthetic and editorial style materials released in hard
    copy and Web forms.

All releases shall have the prior approval of the PI.

**4.4 Carnegie Institution of Washington**

The CIW Public Relations Office will be the prime point of contact with
the public and the media for the MESSENGER science activities. Press
releases with science content will be delegated to the CIW or JHU/APL
Media Relations Office for release as deemed appropriate by the PI.
Release shall be only with the PI's prior consent.

**4.5 Applied Coherent Technology**

ACT is the MESSENGER sub-contractor for the SOC. Their responsibilities
include providing the SOC software that enables the Science Team to
access the mission data, receiving all standard products from the
Science Team and storing them in PDS-compliant formats, and delivering
all standard products from the Science Team to the PDS. They are
responsible for producing all EDRs in a format usable to the Science
Team and acceptable by the PDS for archiving. They provide cleaned and
merged telemetry for all instruments and the spacecraft for use in
producing the higher-level standard products by the Science Team.

**5.0 Data Flow within the MESSENGER Project**

Figure 2 summarizes and maps the flow of data and information within the
MESSENGER project for achieving its science goals and objectives. The
mission science objectives correspond to measurement requirements. It is
the task of the SOC to translate these measurement requirements into
instrument observation plans and commands. These are transferred to the
Mission Operations Center (MOC) for integration with the spacecraft and
navigation commands and relayed to the spacecraft through the DSN. The
resulting observations are then downlinked from the spacecraft through
the DSN back to the MOC. The MOC then transfers all science data and
related navigation, commanding history, and housekeeping (both
instrument and spacecraft housekeeping) information to the SOC. The SOC,
through interactions with the Science Team, Instrument Scientists, and
Instrument Engineers, then performs data validation, calibration, and
product generation.

**5.1 Mission Operations Center (MOC)**

The data management responsibilities of the MOC include:

-   merging instrument commanding with spacecraft and navigation
    commanding for upload to the spacecraft through the DSN

-   receiving all science data from the spacecraft through the DSN

-   providing the SOC with the downlinked science data, related
    telemetry, navigation, and housekeeping data

-   working with the Navigation Team and the NAIF node of the PDS to
    provide SPICE information to the SOC for higher-level data product
    production and archive.

**5.2 Navigation Team**

The data management responsibilities of the Navigation Team include:

-   supplying optical navigation observing requirements to the imaging
    team for inclusion in the observation command load for the MDIS
    instrument

-   supplying accurate SPICE information to the SOC for Science Team use
    in data product generation and for data archiving.

**5.3 Mission Design and G&C Team**

The data management responsibilities of the Mission Design and G&C Team
include

-   working with the Navigation Team for orbital maneuver design and
    defining orbital maneuver targets

-   providing orbital maneuver information and parameters to the MOC for
    execution .

**5.4 Science Operations Center (SOC)**

The SOC is managed under the auspices of the Project Scientist. The
management of the SOC is led by ACT, with key roles played by JHU/APL
and the Science Team. The SOC is physically located at JHU/APL.

The core of the data management responsibilities are those of the SOC.
They include

-   support for ground and in-flight instrument calibrations

-   science planning, including instrument operations and commanding,
    data acquisition and validation, and maintaining a status report on
    the mission's progress in meeting its science objectives

-   dissemination of the data to the MESSENGER Science Team

-   keeping an internal archive of the science data products produced by
    the Science Team for later archiving to the PDS

-   archiving of all mission data (including instrument calibration
    data, and all standard data products)

-   dissemination of selected data products to the project's
    education/public outreach effort.

**5.5 Science Team**

The Science Team receives all mission science data and supporting
ancillary data. Their main responsibility is the scientific analysis of
the MESSENGER data set and the production of the higher level data
products described in Section 3. The Science Team is responsible for the
delivery of all CDRs, DDPs, and DAPs to the SOC for archiving by the
PDS.

The Science Team is responsible for defining data quality assessment
criteria for the SPG. The SPG, whose members are drawn in part from the
Science Team, will apply these data quality assessment criteria to
fulfill some of the SOC data validation requirements. The Science Team
provides guidance to the SPG for meeting the mission science objectives
through the Science Steering Committee.

**6. Policies For Release Of Data And Public Information**

**6.1 Data Rights and Release Policy**

Because of the expected widespread scientific and public interest in new
results from Mercury and the strong commitment of the MESSENGER project
to releasing data on a timely basis, it is important to establish a
clear policy for data dissemination to both the general public and the
science community. The MESSENGER project recognizes the importance of
disseminating the data and measurements it will acquire during its
mission in a prompt and timely fashion. As stated in the MESSENGER CSR,
the project is committed to providing all mission data as soon as
processing and validation are complete, thus insuring the highest
quality control on all data released.

Table 7 provides the schedule for delivery of EDRs from the MESSENGER
project to the PDS, as specified in the MESSENGER CSR. The CSR does not
specify a schedule for delivery of the Venus flyby data. Based on the
Mercury flyby delivery schedule, the MESSENGER project will delivery all
Venus flyby data after the completion of the second Venus flyby. The
MESSENGER CSR commits the project to delivering all RDRs to the PDS
within 12 months of the end of mission.

Table 7. EDR Delivery Schedule to PDS

  ------------- ---------------------------- ----------------------------
  **Mission     **PDS Delivery Date in CSR** **MESSENGER Planned Delivery
  Data**                                     Date**

  Venus flyby 1 Not specified                6 months after 2^nd^ Venus
                                             flyby encounter

  Venus flyby 2 Not specified                6 months after 2^nd^ Venus
                                             flyby encounter

  Mercury flyby After 2^nd^ Mercury flyby    6 months after 2^nd^ Mercury
  1             encounter                    flyby encounter

  Mercury flyby After flyby encounter        6 months after 2^nd^ Mercury
  2                                          flyby encounter

  Mercury orbit 6 months after end of        6 months after end of
                mission (18 months after     mission (18 months after
                Mercury orbit insertion)     Mercury orbit insertion)
  ------------- ---------------------------- ----------------------------

The generation/validation time period for standard data products is
defined to be the period from receipt of science packets containing raw
data at instrument processing facilities until release of archive
volumes to the PDS. The archive volumes will include, as appropriate,
all EDRs, RDRs, ancillary data, relevant software, and documentation
describing the generation of the products.

The calibration data, a subset of ancillary data, is required for the
interpretation and understanding of the science data set. The
calibration data has both on-ground and in-flight components. The
delivery schedule of this subset of ancillary data is as follows:

-   On-ground calibration data will be provided to the SOC at least 3
    months prior to launch, including all relevant documentation and
    labels.

-   On-ground calibration data will be delivered and archived to the PDS
    by the SOC within six months after launch.

-   In-flight calibration data collected to date will be delivered to
    the SOC prior to the first Mercury flyby, including all relevant
    documentation and labels.

-   In-flight calibration data collected to date will be delivered and
    archived to the PDS by the SOC within six months of the second
    Mercury flyby.

-   Subsequent in-flight calibration data will be delivered to the SOC
    prior to the end of the mission.

-   A final delivery of calibration data will be made to the PDS via the
    SOC within six months of the end of mission, in conjunction with the
    delivery to PDS of the Experimental Data Records (EDRs). This will
    include references to calibration papers with complete descriptions
    of data and calibration algorithms published in peer-reviewed
    literature.

To ensure rapid dissemination of new and significant information, the PI
and the PS will coordinate release of a significant subset of data
earlier as a form of public outreach and education. These releases will
typically be available within a week of data receipt. Postings on the
World Wide Web (WWW) will be used as a cost-effective way for widespread
dissemination of these special products. The posted data may include
images, derived spectra, topographic information, and other forms of
data that illustrate new and significant results. Postings will include
documentation. These data releases will conform to the Public
Information Release Policy (Section 6.2 below).

During the generation/validation period, any scientific use and analysis
of raw and derived products from a particular instrument, use of results
from unpublished papers derived from such analysis, or posting of
scientific analysis of data on the WWW for public outreach and
education, requires the explicit agreement of the PI.

In the event of anomalies, data should be archived using stated
policies, unless observational, personnel, and/or financial constraints
force the need for a longer period between data receipt and transfer of
archives to the PDS.

**6.2 Public Information Release Policy**

The guidelines for releasing materials to the public, as stated in the
MESSENGER CSR, are as follows.

-   Preliminary data will be released on a public web site within \~72
    hours of downlink.

-   Public dissemination of selected images and data will occur
    immediately following calibration with the best currently available
    calibration algorithms.

-   Optimal use will be made of the World Wide Web (WWW) to provide
    results to associated educational and outreach endeavors.

Public information release includes press conferences, postings on the
WWW, and printed materials concerning both mission operations and
scientific analyses. Additional policy statements for Public Information
Release for the MESSENGER project are:

-   Information concerning spacecraft and instrument anomalies may be
    released only by the MESSENGER Project Office, in coordination with
    NASA Headquarters and the PI. Information concerning significant
    scientific results may be released during press conferences, press
    releases organized by the MESSENGER Project Office and the JHU/APL's
    Media Relations Office, and on the WWW, and in coordination with
    NASA Headquarters and relevant members of the Science Team, but only
    with the concurrence of the MESSENGER PI.

-   Information concerning scientific results from any instrument study
    may be released by a Co-Investigator before it is deposited in the
    PDS, but only with the concurrence of the MESSENGER PI.

-   The MESSENGER Project Office must receive, 48 hours in advance, a
    copy of any released material (e.g., images, spectra, captions,
    summary of results), a schedule for the release, and a statement of
    the mechanisms for release. The intent is not to require concurrence
    for the release, but only to make sure that the MESSENGER Project
    Office, JHU/APL's Media Relations Office, and NASA Headquarters are
    informed of the releases before they happen.

The primary tool for dissemination of the MESSENGER data set to the
general public will be the WWW. An outline of the MESSENGER web site is
included in Appendix A. Those portions of the web site pertaining to
data dissemination are (1) the Image of the Day, (2) the Mission/Monthly
Status Reports, (3) the Mission/Movies & Animation, (4) the Science
Operations, (5) the News Room/Gallery/Images, and (6) the News
Room/Mission Information/Press Kit. Also part of the MESSENGER web site
is a section dedicated to education. The purpose of this section is to
inform the general public about the science and engineering aspects of
our mission. It will provide tools for educators and opportunities for
interactions with the MESSENGER team. This education section of the web
site is focused on the learning experience rather than dissemination of
data.

*Image of the Day*

Selected images and data will be released on a daily basis after
calibration with the best available calibration algorithm at the time
the images and data are downlinked from the spacecraft. Captions will be
included with the released images and data that describe the material
and its scientific importance. An archive of the "Image of the Day" will
be maintained and accessible through several venues on the web site.

*Mission/Monthly Status Reports*

Engineering and science status reports to NASA Headquarters will be
produced on a monthly basis. The most current report will be available
on this portion of the web site, with an archive to past reports. These
reports may include new science developments and discoveries and will
discuss the latest science results from the mission.

*Mission/Movies & Animation*

The MESSENGER project will produce animations describing the mission and
movies generated from images acquired by the spacecraft. Several image
acquisition sequences are being planned with the goal of generating
movies from the images. These will be made available to the general
public through the web site.

*Science Operations*

This portion of the MESSENGER web site will contain five separate
sections dealing with the status and dissemination of the MESSENGER
mission data and data products. The first section, Observation Planning,
is a description of the planned observations on a monthly time schedule.
The second section, Data Status, focuses on the data acquisition
process: what observations are on the solid-state data recorder, which
observations have been downlinked, and a pointer to currently processed
and validated raw data (experimental data records). The third section,
Science Publications, is focused on data and data products released
through peer-reviewed journals. This will point to a reference list of
published papers (with links to the relevant journals) in addition to a
sub-section containing published data products in a downloadable
electronic format. The fourth section, Science Presentations, will
contain a calendar of scheduled talks relevant to MESSENGER science
questions and an archive of science meeting abstracts and selected
viewgraph sets from the MESSENGER Science Team. The final section,
Science Focus: Month Year, will be a monthly science discussion
highlighting a member of the Science Team discussing interesting science
returns from the MESSENGER mission. This site may link to the
Education/MESSENGER classroom/Community Forum/Scientist of the Month
portion of the web site.

*News Room/Gallery/Images*

The intent of the News Room section of the web site is to provide an
information resource for the media. The Gallery/Image section of this
resource will point to the "Image of the Day" archive.

*News Room/Mission Information/Press Kit*

The MESSENGER project will be producing press release materials in
association with major mission events, press conferences, and scientific
meetings. For example, press release materials (Press Kits) will be
generated in association with launch, flyby encounters, and Mercury
orbit insertion. Electronic versions of these materials will be made
available to the general public via this portion of the MESSENGER web
site.

While the MESSENGER project is committed to provide information to the
general public in a timely fashion, the MESSENGER project does not plan
to archive any education and public outreach products with the PDS. The
MESSENGER Education/Public Outreach Team will maintain and archive all
E/PO products.

**6.3 Release Policy to Science Community**

The guidelines for releasing materials to the scientific community, as
stated in the MESSENGER CSR, are as follows.

-   All data, applicable housekeeping, and calibration algorithms will
    be released to the PDS within six months of the end of mission
    (flyby data will be released within six months of the second flyby).

-   Data products of scientific interest will be disseminated in
    electronic and printed formats.

-   In parallel with final archiving at the PDS, scientific results will
    be shared with the science community via scientific meetings and
    peer-reviewed publications.

-   In recognition of the necessity and responsibility for providing
    fully documented data sets in a timely manner to maximize the
    science return from the mission, optimal use will be made of the PDS
    and the WWW to provide results to the scientific community.

Dissemination or data release in electronic format is defined as release
through the WWW, whereas the release in printed format (excluding
peer-reviewed publications) is defined as the release of selected
materials in hardcopy form, such as through press releases, press kits,
and education program materials. Table 8 (taken from the CSR) summarizes
the deliverables to the PDS along with delivery guidelines and schedule.

**Table 8. Data Product Delivery** (taken from CSR Table F-6-2)

  ----------------------------- -------------- -------------- ----------------
  **Deliverable**               **Source**     **Web          **Submission**
                                               Display**      

  Flight instrument data        SOC            Immediate      EOM + 6 mo.

  Navigation and housekeeping   SOC            Immediate      EOM + 6 mo.
  data                                                        

  Data products, Table D-1-1    Science Team   Monthly        EOM + 1 yr

  Analysis products, Table      Science Team   Receipt + 2mo. EOM + 1 yr
  D-1-1                                                       
  ----------------------------- -------------- -------------- ----------------

The MESSENGER project is committed to providing all mission data to the
scientific community as soon as processing and validation are complete,
thus insuring the highest quality control on all data released to the
science community. The primary mechanism for data distribution and
release is through data archiving with the PDS. The PDS was established
for the purpose of archiving all NASA mission data and is the primary
venue for MESSENGER's data release policy to the science community. All
scientific data and data products will be delivered to the PDS through
the MESSENGER SOC. While it is the responsibility of the MESSENGER
Science Team and the cognizant Co-Is to generate all data products, the
delivery of these products will be conducted through the SOC.

In concert with the data archiving process, data and analysis products
of scientific interest will be disseminated in electronic and printed
formats and scientific results will be shared via scientific meetings
and peer-reviewed publications.

The MESSENGER CSR commits to the delivery of all EDRs to the PDS within
six months of the end of mission. The schedule of EDR deliveries is
summarized in Table 7. While the CSR does not specify a delivery date
for the Venus flyby observations, it is the intent of the MESSENGER
project to submit the EDRs from these set of observations within six
months of the second Venus flyby.

In parallel with the archival process being conducted through the PDS,
EDRs will be made available through the MESSENGER public web site via
the Science Operations/Data Status section of the site. Processed and
validated EDRs for completely downlinked days will be made available to
the public and scientific community through a link from this site to a
project-supported archive. In this manner, flight instrument data are
made available immediately (see Table 8) in electronic format via the
WWW.

The MESSENGER CSR states that all data products will be archived with
the PDS within 12 months of the end of mission. MESSENGER data products
include CDRs, DDPs, and DAPs. The MESSENGER project is committed to
deliver a final calibration algorithm and calibrated post-launch data
within 12 months of the end of mission.

In parallel with the archiving of the MESSENGER EDRs and CDRs with the
PDS, the DDPs and DAPs will be presented at scientific meetings and
published in peer-reviewed journals. Commensurate with their
presentation and publication the DDPs and DAPs will be released in
electronic format to the science community through the public web site.
A portion of the public web site, titled Science Operations, will focus
on the dissemination of scientific results. This portion of the public
web site has a section (Data Status) where currently processed and
validated EDRs are available. In another section (Science Publications),
an archive will be maintained of published DDPs and DAPs. The Science
Operations/Science Publications portion of the web site may include
references to copyrighted articles (with pointers to the journal web
sites), copies of meeting abstracts, and copies of presentation
materials. These DDPs and DAPs will be released via the web site within
2 weeks of publication or presentation.

**6.4 Data Release Acknowledgement Policy**

In any release of data or information as described in Sections 4.1 and
4.2 above, appropriate credit will be given to all entities involved,
including the Science Team member(s), his or her home institution,
JHU/APL, supporting institutions (as appropriate), and NASA. The credit
will appear on public web sites that contain data releases and on
documentation that accompanies the data products.

**6.5 International Traffic in Arms Regulations (ITAR)**

The information referred to in this document is being acquired through
fundamental research in science and engineering at an accredited
institution of higher learning in the U.S. The type of information being
placed in the public domain is information that is ordinarily published
and shared broadly in the scientific community. The information is not
restricted for proprietary reasons. The U.S. Government has not placed
specific access and dissemination controls on the information. (See
\[CFR\] Section 120.11(8).)

**7.0 Archive Process**

The MESSENGER archive will contain standard data products from each of
the instruments, navigation and geometry data from the SPICE information
system, ancillary data, software, and sufficient documentation to ensure
that future scientists can understand and use the archive. The science
data products form the core of the archive and are discussed in Section
3.

Production of this archive involves design of the archive structure and
contents, generation of the archive components, validation, and final
packaging and delivery. The archive production is described in detail in
the AGVDP. High-level descriptions of the planning and design,
generation, validation, and delivery are presented below.

**7.1 Planning and Design**

The total volume of EDRs expected to be downlinked from the MESSENGER
mission is on the order of 70 Gbits. The final MESSENGER archive to the
PDS may be on the order of 300 to 400 Gbits. The archive will be
delivered using a physical medium such as CDs or digital versatile disks
(DVDs), as appropriate. The data will be ordered first by time, then by
instrument, and further divided by type of data, if relevant. Figure 3
illustrates the structure of a typical volume of the archive.

The details of what components are included in the archive and how they
are grouped into data sets, subdirectories, and files comprise the
design of the archive. The format and content of data products are
described in detail in the individual instrument SIS documents, which
have been created by the SOC lead with inputs from the relevant
Instrument Scientists and cognizant Co-Is. The format and content of the
archive volumes are described in the Archive Generation, Validation, and
Dissemination Plan (AGVDP), which is generated by the MESSENGER DAWG.
Archive plans within the AGVDP will be developed for each instrument in
cooperation with the SOC to ensure that archive generation is
accomplished on schedule and to provide a forum for validation.

Preparation for generating project data archives involves designing the
data products and the archive volumes on which they will be stored and
developing the systematic generation, validation, and distribution
procedures for these archive volumes. The plans shall be documented in
the AGVDP.

The PDS has developed a set of software tools useful for generating
archive volumes. They include tools for reading, writing, and validating
labels for data products, generating data dictionaries and index tables,
and validating archive volumes. For more information see the PDS
World-Wide Web site at *http://pds.jpl.nasa.gov*/.

**Figure 4. General structure of a typical volume of the MESSENGER
archive.**

**7.2 Generation**

An *archive* consists of one or more data sets along with all the
documentation and ancillary information needed to understand and use the
data. Thus defined, an archive is a logical construct that is
independent of the medium on which it is stored.

An *archive volume* is a unit of medium on which an archive is stored;
for example, one CD-ROM. When an archive spans multiple volumes, they
are called an archive volume set. Usually the documentation and some
ancillary files are repeated on each volume of the set, so that a single
volume can be used alone.

Whole or partial archives may be placed online for convenient
distribution via the Internet. However, to ensure long-term viability,
archives must also be stored offline on physical archive volumes. The
choice of storage medium will depend on available technology. It should
be a stable, industry-standard medium intended for long-term storage.
The standard media for long-term storage are CD-ROMs and DVD-ROMs.

Responsibility for generating archive components is specified in Section
4. Science data products will be generated in PDS‑compliant formats.
Each data file (data table or image file) will be in a format approved
by PDS and will be accompanied by a PDS \"label,\" which describes the
content and structure of the accompanying data file. Navigation and
geometry data necessary to interpret the data (e.g., spacecraft
ephemeris and attitude records, command histories, and spacecraft
housekeeping files) will be provided as ancillary archive components.
The source code of all software to be provided with the archive will be
collected and documented. In addition, files documenting the archive
components will be prepared by the parties generating the data. In
general, all information necessary to interpret and use the data are to
be included in the archive.

The PDS \"catalog objects\" are files that document the mission,
spacecraft, instruments, and data products. The catalog objects take the
form of templates which must be filled out with prescribed information.
The required catalog objects are the "mission template," describing the
MESSNEGER mission as a whole, the \"instrument host template\"
describing the spacecraft, one instrument template for each instrument,
and one data set template for each data set. These templates will
contain information needed to document the archive and enable future
scientists to make correct use of the data when mission personnel are no
longer available to support them. The PDS will fill in the formal
portions of the catalog objects, requiring only text descriptions of the
mission, spacecraft, instruments, and data sets from MESSENGER.

The Navigational and Ancillary Information Facility (NAIF) will assist
the SOC in generating an archive volume set of all SPICE (Navigation and
Geometry) data.

**7.3 Validation**

Data validation falls into two types, validation of the data itself and
validation of the compliance of the archive with PDS archiving
requirements. The first type of validation will be carried out by the
Science Team, and the second will be overseen by the PDS, in
coordination with the Science Team.

The formal validation of data content, adequacy of documentation, and
adherence to PDS archiving standards is subject to an external peer
review. The peer review will be scheduled and coordinated by the PDS.
The peer review process may result in \"liens,\" actions recommended by
the reviewers or by PDS personnel to correct the archive. All liens must
be resolved by the dataset provider: the SOC for Level-1 data, and the
Science Team for higher-level data products, calibration data, and
calibration algorithms. Once the liens are cleared, PDS will do a final
validation prior to packaging and delivery.

The SOC will periodically report results of validation to the Science
Steering Committee. If the volumes are approved for release by the
Project, then the SOC will transfer the archives to the PDS, based on
the release schedule specified by the project\'s Archive Generation,
Validation, and Distribution Plan.

**7.4 Delivery**

The delivery schedule for archive products is discussed in Section 3.
However, a summary of the archive delivery schedule is as follows:

-   all on-ground calibration data will be delivered within 6 months of
    launch

-   all in-flight calibration data will be delivered within 12 months of
    End of Mission (EOM)

-   all Venus flyby data will be delivered within 6 months of the 2^nd^
    Venus flyby

-   all Mercury flyby EDRs will be delivered within 6 months of the
    2^nd^ Mercury flyby

-   all post-launch EDRs will be delivered within 6 months of EOM

-   all post-launch CDRs, DDPs, and DAPs, along with final calibration
    algorithms, will be delivered within 12 months of EOM.

**8.0 Definitions of Terms**

**Ancillary Data** -- Non-science data need to generate calibrated or
resampled data. Any information needed to create any of the standard
data products, such as CDRs, DDPs, and DAPs.

**Archive** -- An archive consists of one or more data sets along with
all the documentation and ancillary information needed to understand and
use the data. An archive is a logical construct independent of the
medium on which it is stored.

**Archive Volume, Archive Volume Set** -- A volume is a unit of medium
on which data products are stored; for example, one CD-ROM. An *archive
volume* is a volume containing all or part of an archive; that is, data
products plus documentation and ancillary files. When an archive spans
multiple volumes, they are called an *archive volume se*t. Usually the
documentation and some ancillary files are repeated on each volume of
the set, so that a single volume can be used alone.

**Calibrated Data Records** -- CODMAC Level-2 data that have been
located in space and may have been transformed (e.g., calibrated,
decompressed, rearranged) in a reversible manner and packaged with
needed ancillary and auxiliary data (e.g., radiances with the
calibration equations applied).

**Data Product** -- A labeled grouping of data resulting from a
scientific observation, usually stored in one file. A product label
identifies, describes, and defines the structure of the data. An example
of a data product is a planetary image, a spectrum table, or a time
series table.

**Data Set** -- An accumulation of data products. A data set together
with supporting documentation and ancillary files is an archive.

**Derived Data Products** -- CODMAC Level 3 or 4 standard data products.
Irreversibly transformed (e.g., resampled, remapped, calibrated) values
of the instrument measurements (e.g., radiances, magnetic field
strength).

**Derived Analysis Products** -- CODMAC Level 3 through 5 standard data
products. Irreversibly transformed (e.g., resampled, remapped,
calibrated) values of the instrument measurements (e.g., radiances,
magnetic field strength). Data that have been resampled and mapped onto
uniform space-time grids. The data are calibrated and may have
additional corrections applied.

**Engineering Products** -- A subset of Ancillary Data, often in the
form of instrument settings (such as voltages, current, and
temperature), and spacecraft health status.

**Experimental Data Records** -- NASA Level 0 data for a given
instrument; raw data.

**Navigation Data** - A subset of Ancillary Data, often in the form of
SPICE files, that aid the interpretation and processing of standard data
products and are needed for producing the higher-level standard data
products, such as the DDPs and DAPs.

**Packetized Data Records** -- Telemetry data stream as received at the
ground station, with science and engineering data embedded.

**Processed Data** -- CODMAC Level 3 or higher standard data products.

**Project Data** -- Any data products produced by the MESSENGER project
for archive to the PDS.

**Raw Data** -- Same as Packetized Data Records

**Raw Science Data** -- Same as Raw Data and Packetized Data Records.

**Reduced Data Records** -- Science data that have been processed from
raw data to NASA Level 1 or higher. See Table 3 for definitions of
processing levels.

**Science Data** -- PDRs, EDRs, and RDRs that have scientific value.

**SPICE Data** -- A suite of elemental ancillary data sets, often called
kernels. They include spacecraft ephemeris, planet/satellite
ephemerides, instrument information, camera orientation, and event
information.

**Standard product** -- A data product that has been defined during the
proposal and selection process and that is contractually promised by the
PI as part of the investigation. Standard data products are generated in
a predefined way, using well-understood procedures, and processed in
\"pipeline\" fashion.

**9.0 References**

Arvidson, R., E. Guinness, and S. L. Dueck, The Planetary Data System,
*Remote Sensing Rev*. ***9***,\
255-269 (1994).

Boynton et al., Science, (2002) Distribution of Hydrogen in the Near
Surface of Mars: Evidence for Subsurface Ice Deposit, 297, pp. 81-85

Feldman et al, Nucl Instr. and Methods, (1995) Calibration of a space
thermal/epithermal neutron detector: the Mars Observer gamma-ray
spectrometer anticoincidence shield, A362, pp. 561-575

Gold, R. E., *et al*., The MESSENGER Mission to Mercury: Scientific
Payload, *Planetary Space Science* **49**, 1267-1479 (2001).

McMahon, S. K., Overview of the Planetary Data System, *Planetary and
Space Science,* **44**, 3-12 (1996).

*MErcury: Surface, Space ENvironment, GEochemistry, Ranging; A Mission
to Orbit and Explore the Planet Mercury,* MESSENGER Concept Study Report
(1999).

Santo, A.G., *et al*., The MESSENGER Mission to Mercury, Spacecraft and
Mission Design, *Planetary and Space Science* **49**, 11481-1500 (2001).

Solomon, S.C., *et al*., The MESSENGER Mission to Mercury, Scientific
Objectives and Implementation, *Planetary and Space Science* **49**,
1445-1465 (2001).

**10.0 Acronyms**

Table 9. Acronym defintions

  ------------- ---------------------------------------------------------
  **Acronym**   **Definition**

  ACT           Applied Coherent Techonolgies

  AGVDP         Archive Generation Validation and Dissemination Plan

  AM            Atmosphere and Magnetosphere Group

  APL           Applied Physics Laboratory

  BP            Borated Plastic

  BST           Burst data

  CDR           Calibrated Data Record

  CIW           Carnegie Institution of Washington

  CODMAC        Committee On Data Management And Computation

  CSR           Concept Study Report

  DAP           Derived Analysis Product

  DAWG          Data Archive Working Group

  DDP           Derived Data Product

  DEC           Declination

  DN            Data Numbers

  DNL           Differential Non-Linearity

  DSN           Deep Space Network

  EDR           Experimental Data Record

  EPPS          Energetic Particle and Plasma Spectrometer

  EPS           Energetic Particle Spectrometer

  FIPS          Fast Imaging Plasma Spectrometer

  FITS          Flexible Image Transport Standard

  FOV           Field of View

  GC            Geochemistry Group

  GDS           Ground Data System

  GG            Geology Group

  GP            Geophysics Group

  GRNS          Gamma-Ray and Neutron Spectrometer

  GRS           Gamma-Ray Spectrometer

  GS            GeoScience

  InGaAs        Indium Gallium Arsenide

  INL           Integral Non-Linearity

  JHU/APL       The Johns Hopkins University/Applied Physics Laboratory

  LHK           Low-rate Housekeeping

  LSB           Least Significant Bit

  MAG           Magnetometer

  MASCS         Mercury Atmosphere and Surface Composition Spectrometer

  MD            Mission Design

  MDIS          Mercury Dual Imaging System

  MESSENGER     MErcury Surface Space ENvironment GEochemistry Ranging

  MLA           Mercury Laser Altimeter

  MOC           Mission Operations Center

  NAIF          Navigation and Ancillary Information

  NAV           Navigation

  NSSDC         National Space Science Data Center

  NS            Neutron Spectrometer

  PAD           Pulse Amplifier Discriminator

  PDR           Packetized Data Record

  PDS           Planetary Data System

  PHA           Pulse-height analysis

  PI            Principal Investigator

  PLR           Project Level Requirements

  PPI           Planetary Plasma Interactions

  PS            Project Scientist

  RA            Right Ascention

  RDR           Reduced Data Record

  RS            Radio Science

  S/C           Spacecraft

  SIS           Software Interface Specification

  SOC           Science Operations Center

  SPG           Science Planning Group

  SPICE         Spacecraft ephemeris, Planet/satellite ephemeris,
                Instrument information, Camera orientation, Event
                information.

  SSC           Science Steering Committee

  SSD           Standard Science Data

  SSR           Solid State Recorder

  ST            Science Team

  TTSP          Time To Second Pulse

  UTC           Universal Time ???

  UVVS          Ultra-Violet Visible Spectrometer

  VIRS          Visible Infrared Spectrometer

  XRS           X-Ray Spectrometer
  ------------- ---------------------------------------------------------