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W. W. Hansen Experimental Physics Laboratory

STANFORD UNIVERSITY

STANFORD, CALIFORNIA 94305 - 4085

Gravity Probe B Relativity Mission

**S1016, Revision -**

May 15, 2007

Data Archive Plan

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Tom Langenstein ITAR Assessment Performed, ITAR Control Req'd? □ Yes □
No

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**Alan Smale Tony Lyons**

**Program Manager, Gravity Probe B Program Manager, Gravity Probe-B**

**NASA Headquarters NASA Marshall Space Flight Center**

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**Ed Grayzeck Francis Everitt**

**Head, National Space Science Data Center Principal Investigator,
Gravity Probe-B**

**NASA Goddard Space Flight Center Stanford University**

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**Bill Bencze Jennifer Spencer**

**Program Manager, Gravity Probe B Data Archive Lead, Gravity Probe-B**

**Stanford University Stanford University**

+-----------------+-----------------+-----------------+-----------------+
| **Date**        | *               | **Reasoning**   | **Revision**    |
|                 | *Sections/Pages |                 |                 |
|                 | Affected**      |                 |                 |
+-----------------+-----------------+-----------------+-----------------+
| **2/2006**      | **All**         | **First draft** | **Preliminary** |
+-----------------+-----------------+-----------------+-----------------+
| **8/2006**      | **All**         | **Revisions to  | **Preliminary** |
|                 |                 | draft**         |                 |
+-----------------+-----------------+-----------------+-----------------+
| **1/2007**      | **All**         | **Revisions per | **Preliminary** |
|                 |                 | NSSDC           |                 |
|                 |                 | comments**      |                 |
+-----------------+-----------------+-----------------+-----------------+
| **5/2007**      | **Table 6.1,**  | **Revisions to  | **Preliminary** |
|                 |                 | Guide Star      |                 |
|                 | **Appendix A**  | data,           |                 |
|                 |                 | schedule**      |                 |
+-----------------+-----------------+-----------------+-----------------+

Table of Contents

[Introduction 4](#introduction)

[Purpose 4](#purpose)

[Scope 4](#scope)

[Applicable Documents 4](#applicable-documents)

[Document Change Control 4](#document-change-control)

[Mission Overview 4](#mission-overview)

[Archive Structure 5](#archive-structure)

[Archive Terms Defined 5](#archive-terms-defined)

[Overview of the Archiving Functions
5](#overview-of-the-archiving-functions)

[Archive Design 6](#archive-design)

[Generation of Archive 6](#generation-of-archive)

[Validation of Archive 7](#validation-of-archive)

[Delivery 7](#delivery)

[Further Information 7](#further-information)

[Roles and Responsibilities 7](#roles-and-responsibilities)

[Responsibilities of Gravity Probe B
7](#responsibilities-of-gravity-probe-b)

[Responsibilities of the NSSDC 7](#responsibilities-of-the-nssdc)

[Science Data Archive Products 8](#science-data-archive-products)

[Raw Data 8](#raw-data)

[Level 0 8](#level-0)

[Level 1 8](#level-1)

[Level 2 8](#level-2)

[Level 3 9](#level-3)

[Format of Science Data Files 9](#format-of-science-data-files)

[Documents 13](#documents)

[Specifications 13](#specifications)

[Drawings 13](#drawings)

[Test Documents/As-Run Procedures 13](#test-documentsas-run-procedures)

[Photographs 13](#photographs)

[Web Site 13](#web-site)

[Schedule for Archive Generation, Validation, and Delivery.
13](#schedule-for-archive-generation-validation-and-delivery.)

[GP-B Data Release Policy. 14](#gp-b-data-release-policy.)

[Appendix A: Guide Star Data from the SAO
15](#appendix-a-guide-star-data-from-the-sao)

[Appendix B: GP-B Acronyms 18](#appendix-b-gp-b-acronyms)

[Appendix C: ITAR 20](#appendix-c-itar)

# Introduction

## 

## Purpose

This document provides a high-level description of archival data
products and archiving methodology at all levels for the Gravity Probe B
(GP-B) Mission.

The data products specified in this document are obtained from the
science instruments and subsystems on board the GP-B spacecraft, and
include the results of any ground data processing carried out by the
GP-B Data Processing team (DP). At all levels of data processing,
several additional data are also needed. These may include the results
of pre-flight tests or calibration experiments carried out by the GP-B
mission. These may also include specifications, acceptance data,
drawings and other engineering papers. Further, certain science data are
collected by various terrestrial observatories specifically for the GP-B
mission, and are acquired through existing, independent data systems
outside the GP-B project. All of these data products are discussed in
this document. However, standard data products, commonly available to
the science community and independently documented, are not specified in
this document.

## Scope

This document is applicable to all science and supplementary data
resulting from the Gravity Probe B spacecraft. This document is
subordinate to the GP-B Data Management Plan (S0331). Separate
agreements, including a Memorandum of Understanding, established with
the National Space Sciences Data Center (NSSDC) and Marshall Space
Flight Center (MSFC), broadly address data archiving.

## Applicable Documents

Gravity Probe B Data Management Plan (S0331)

Memorandum of Understanding between Gravity Probe B and the NSSDC

Stanford post processing operations for Science Mission Data (S0401)

## Document Change Control

This document is under change control once all parties sign it. All
signatories must approve each revision.

# Mission Overview

Gravity Probe-B was begun in 1959, funded by NASA since 1963
(retroactively from 1964). The purpose of the Gravity Probe B Relativity
Mission satellite is to measure two relativistic effects on nearly
perfect gyroscopes. Einstein's General Theory of Relativity precisely
predicts both of these effects; the spacecraft measurements are an
experimental test of the General Theory of Relativity.

The two measured relativistic effects are the geodetic effect, which is
due to the gravitational interaction of the spinning gyroscope and its
orbital angular momentum about the earth, and the motional or
frame-dragging effect which is due to the gravitational interaction
between the spinning gyroscope and the angular momentum of the earth.
The geodetic effect is predicted to cause a drift rate of 6.6 arc
seconds per year in the plane of the orbit for a gyroscope in a \~640 km
circular orbit, and the motional effect is predicted to cause a drift of
the 41 milli-arc seconds per year in a direction perpendicular to the
plane of the orbit.

The requirement for the overall accuracy of the Gravity Probe B
Experiment is to measure the drift rate of each of the four gyroscopes
to an accuracy of 0.5 milli-arc-seconds per year. At this level, the
frame dragging effect will be measured to an accuracy of 1%, and the
geodetic effect will be measured to an accuracy of 1 part in 10,000. A
measurement of the drift rate of the gyroscopes at this level of
accuracy will be the most accurate non-null experimental test of the
General Theory of Relativity. Present estimates of the overall accuracy
of the experiment indicate that it will be possible to measure the drift
rates significantly better than 0.5 milli-arc-seconds per year.

The Gravity Probe B spacecraft was launched aboard a Boeing Delta II
launch vehicle at 9:57:24 AM Pacific Daylight Time on April 20, 2004. It
went through an initialization and orbit checkout period of 129 days, a
science data collection period of 352 days, and a calibration period of
46 days, until September 29^th^, 2005. The mission lasted for 527 days.

The telemetry from the satellite contains the essential information to
determine the gyroscope drift rate as well as the health and safety of
the satellite and its subsystems. The Gravity Probe B "Stanford
Post-Processing Operations for Science Mission Data" document (S0401D)
describes the method for processing and storing this information.

# Archive Structure

## Archive Terms Defined

**Archive** - a preservation of data for future use. For this document,
archive pertains only to long-term archives with the NSSDC.

**Archive medium** - a physical device for storing data such as CD, DVD,
or tape. For PDS archives, the medium must be acceptable to NSSDC per
prior arrangement.

**Archive System** -- The archive system is comprised of hardware,
software, procedures, interfaces, and personnel necessary to complete
the archiving of science and ancillary data with the NSSDC.

**Data Processing** -- the team of people responsible for processing
spacecraft data from raw data through Level 1 data, and the same team
members who are responsible for the formal data archive. The group is
chartered to create the GP-B archive.

**Data product** - labeled data resulting from spacecraft or scientific
data. Examples of data products include plots from on-board instruments,
telemetry from the spacecraft or external orbit determination data. A
data product is a component of a data set.

**Data set** - a labeled grouping of data products, metadata,
documentation, and algorithms for applying calibration or further
processing data. Software may also be included.

**Data Object** - A data object is that portion of a data product that
contains the actual data that is described in a data object definition
within an NSSDC label. It is tangible, and can be physically accessed
and manipulated.

**Meta Data** - a label or file that describes one or more science data
objects or products, or indexing information (such as a list of
spacecraft mnemonics and their calibrations).

**NSSDC** -- National Space Sciences Data Center. The primary
organization within NASA responsible for the permanent archive of all
space science data obtained from NASA-sponsored missions. The NSSDC is
located at Goddard Space Flight Center in Greenbelt, Maryland.

**Science Data** -- All data acquired which are used to accomplish
primary science goals of the Gravity Probe B science teams.

**Supplementary Data** - Any data necessary to perform analysis of the
science data. Sometimes referred to as ancillary data.

**Volume** - one or several in a series of media containing archive
data.

## Overview of the Archiving Functions

The purpose of archiving is to provide the GP-B data to the public in a
non-proprietary, agreed-upon format in perpetuity.

The work of archiving shall be done using NSSDC archiving guidelines.
For the GP-B data, those file formats include: text, cdf (common data
format), jpg (for photographs), and pdf (portable document format). GP-B
will archive all of its data and supporting documents and photographs in
these formats.

GP-B will archive support documentation, photographs and science data
per the Data Management Plan (Stanford document S0331A). Science data
will generally be preserved in CDF format.

We may also add additional, more robust data in its original format, as
long as the content of that data is available also in an archive format.
For example, we may include Adobe Photoshop artwork in addition to the
same file in a jpg version. Layered GP-B artwork can be reproduced and
manipulated more easily by artists if it is available in Photoshop, for
the time being.

An instantaneous snap shot of the GP-B web site will be archived at the
NSSDC, along with listings of all data available. Data formats and files
shall be carefully verified before being sent. CDF data will be sent
with a computed CRC (cyclic redundancy check) value so that its data
integrity can be verified upon arrival at the NSSDC.

## Archive Design

The dataset to be archived from the GP-B project is expected to be
approximately two terabytes in size. The archive will be delivered using
a RAID array of hard drives, possibly supplemented with CD or DVD
deliveries, as appropriate. The science data will be ordered by
subsystem first, then by vehicle time and cycle number, and mnemonic.
Section 5 discusses, in detail, the organization of the science data
files. The details of what components are included in the archive and
how they are grouped into data sets, subdirectories, and files comprises
the design of the archive. The upper level structure and contents of the
archive are described in more detail in Section 5. The arrangement of
the final details of the archive down to the file level will not be
specified until more detailed information on the data products and other
components are available.

## Generation of Archive

Responsibility for generating archive components is specified in Section
4. Science data products will be generated in CDF or otherwise accepted
archive‑compatible formats. This requires that each data file (data
table) be in a format recognized by the NSSDC including a header on each
file describing the metadata of the data file. Orbit determination and
event data necessary to interpret the science data (e.g. spacecraft
ephemeris and attitude records, command histories, and operator log
files) will be provided as archive components. These supporting data
will be provided as text, JPEG, FITS or CDF data, depending on the
original format of said data. In addition, files documenting the archive
components will be included. In general, all information necessary to
interpret and use the data are to be included in the archive.

The NSSDC provides for the preservation of the mission, spacecraft, and
instrument information and data products with Archival Information
Packages (AIPs). An AIP consists of a data file and an attribute file
that describes the data file. AIPs facilitate the long term preservation
of archived\
information and are independent of the underlying media types, including
file structures.

## Validation of Archive

Data validation falls into two types, validation of the data itself and
the compliance of the archive with NSSDC requirements. The first type of
validation will be carried out by GP-B archiving staff, and the second
will be overseen by the NSSDC, in coordination with GP-B. Test files
will be sent from time to time for validation to insure that problems in
any early or test deliveries are resolved by the time of the final
archive delivery.

## Delivery 

Delivery of data to the NSSDC shall be in the form of a two-terabyte
RAID array of hard disks. For interim deliveries, data shall be sent to
the NSSDC in a form mutually agreeable to Gravity Probe B and the NSSDC
(See "Responsibilities" in section four).

## Further Information

More information on the GP-B data archive can be found in the GP-B Data
Management Plan, Stanford document S0331 A.

# Roles and Responsibilities

## Responsibilities of Gravity Probe B 

The GP-B team will provide supporting documentation and other material
to ensure the data is usable. GP-B will provide copies of its data to
the NSSDC for permanent archiving in formats acceptable to GP-B and the
NSSDC (and/or it will ensure a parallel flow of data and supporting
material directly to the NSSDC). As GP-B releases new products to the
public, these products will be transmitted to the NSSDC in a mutually
agreed upon manner. For data releases on CD, DVD, or similar media, GP-B
shall provide the NSSDC with a set of these volumes. For data to be sent
electronically, the details of such transfer shall be devised and agreed
upon by GP-B and the NSSDC.

## Responsibilities of the NSSDC

The NSSDC will ensure that the data and supporting material are
effectively accessible by potential users from NASA, other research
communities, and by the public. It is expected that some user access
will be electronic, but the NSSDC will also satisfy most requests for
data to be sent offline. Data transferred electronically between GP-B
and the NSSDC will be subject to quality assurance by the NSSDC and
remote storage of backup copies will be provided by the NSSDC.

The NSSDC will receive NASA-sanctioned GP-B data and supporting material
from GP-B, and it will ensure their long-term preservation against both
media deterioration and technology obsolescence. The NSSDC permanent
archive is not electronically accessible outside the NSSDC. The NSSDC
assumes that the data and supporting material provided by GP-B is
correct. It is the responsibility of GP-B to ensure this correctness
when the data are delivered to the NSSDC.

Upon request from GP-B, the NSSDC will provide copies of data and/or
supporting material in the same format it was provided by GP-B at the
time of the initial delivery.

Upon request from GP-B or the research or public user community, the
NSSDC will replicate and mail data volumes to requesters. It will charge
end users a fee just sufficient to cover the incremental cost of
satisfying the request.

The NSSDC will point users to the appropriate web page as the source of
GP-B data for researchers.

# Science Data Archive Products

## Raw Data

The Raw Data is simply the data, as telemetered from the satellite,
contained in binary files received from SAFS (Goddard Space Flight
Center's Standard Autonomous File Server) in "IPDU" format (see the
Telemetry Data Processing from Raw data to Level 0 in Stanford document
S0401). Raw data may contain duplicates and/or time regression, and may
be missing data. It may also be damaged data due to R/F problems. Any
questionable data (that is marked with unsuccessful Reed-Solomon
encoding, from the wrong spacecraft ID, full of skips and jumps and
unidentified packet types) would be found in Raw Data but not the Level
0 data set.

## Level 0

\"Level 0 Data\" is essentially time-ordered data with communication
artifacts and duplicate records removed.

-   L0 data is as complete a telemetry record as is possible: the time
    correlation table fills in any missing time stamps and all data
    duplications have been removed

-   All data is kept in order of time-sequence

-   All filler data has been removed (APID 2047)

-   The data is separated from transfer frames into binary packets with
    header data

-   All APID types of data are stored in the Level 0 database (except
    APID 2047)

-   Bad/invalid data has been filtered out

## Level 1

Level 1 data is the analog and discrete programmable spacecraft
telemetry:

-   APID 100 only (see S0401 and SCSE-16, section 9 for more
    information)

-   Meaningful in form to human beings (not binary). It is time-stamped
    and time-ordered by mnemonic ID, then by time.

    The differences between \"Level 0 Data\" and \"Level 1 Data\" are:

```{=html}
<!-- -->
```
-   Level 1 data set is the analog and discrete telemetry, which, for
    GP-B, is the data extracted from the APID series 100 packet data
    assembled by the spacecraft into telemetry format table frames and
    sent to the ground. Level 0 holds all APID series data, including
    packet 100 data.

-   Level 1 data is in a meaningful form; source telemetry data numbers
    may be displayed before or after calibrations are applied via TCAD.
    Level 0 is largely binary data.

-   Level 1 is the most refined source of data that may still be
    considered untouched for purposes of data reduction. This is the
    source data to be sent to project engineers and scientists for
    further analysis, along with a small subset of Level 0 data.

## Level 2

Level 2 data is more than a transformation of Level 1 telemetry data.
Level 1 data, along with data from outside sources and re-combinations
of Level 1 data goes through Science Ops pre-processing algorithms to
become Level 2 data.

-   A select subset of the Level 1 data is sent to Science Ops. Filters
    are applied and some additional calibrations are made to the data
    via pre-processing.

-   Other data, such as GPS ephemeris data and Laser Ranging data, are
    combined with the telemetry (Level 1) data, and some monitors from
    the Level 1 data are joined together through pre-processing
    algorithms. Some filtering (lowpass and Kalman filtering for
    example) and FFT's maybe applied.

-   All data is averaged on two-second centers. After all pre-processing
    algorithms are employed, the resulting data set is put into the
    Level 2 database.

-   Level 2 data is considered the cleanest, most complete science data
    set. It is a starting point for analysis.

## Level 3

> Level 3 data is the result of science analysis algorithms being
> performed on Level 2 data. More about the Level 3 data set will be
> included in its accompanying delivery documentation.

## Format of Science Data Files

Telemetry from the Gravity Probe B spacecraft was processed and stored
as detailed in Stanford University document S0401 "Stanford
Post-Processing Operations for Science Mission Data". Please see S0401
for specific understanding of the data and data table relationships.
Additionally, the orbit determination for the mission is described in
S0505, "Interface Definition Document for the Gravity Probe-B Orbit
Determination Function".

UNIX binary files were sent from the Central Standard Autonomous File
Server (C-SAFS) at Wallops, VA, to the Mission Operations Center at
Stanford University for every 32K ground network data pass. These SAFS
files are not in CDF format, and may not be acceptable to the archive.

The mission telemetry was stored to a database, and then exported from
the database to the format known as CDF (Common Data Format) for
purposes of long-term archiving. For more information on CDF file
formats and how to use them, please reference the Goddard Space Flight
Center web pages at <http://cdf.gsfc.nasa.gov/> . This document
henceforth assumes that the user has basic knowledge of CDF formats.

There are two different general types of data: static data and dynamic
data. Static data corresponds to GP-B project metadata; that is, data
about the data. The static (metadata) includes such items as names of
GP-B mnemonics, locations in the telemetry data, packet IDs, format IDs,
ground station IDs, et cetera. Dynamic data is, essentially the
ever-changing spacecraft telemetry from the on-board instruments and
spacecraft bus. Most of the static data files are small, and will be
necessary (per S0401) to understand and use the dynamic files. Static
tables are those data tables that are short, do not change much over
time, and contain no direct spacecraft telemetry. Static tables are
archived in CDF format.

Static data file names are given below in **bold** and their data fields
follow.

Level 0 static data tables

  ----------------- -------------------------------------------------------
  **Table name**    Fields (in the order archived)

  **Station_IDs**   ID_number ID_ASCII

  **APIDs**         APID APID_Name Num_Bytes -

  **Files**         SCT_Cycle Filename Filesize Time_InL0DB Parse_Time
                    IPDUs_Found IPDUs_Processed VTCW_min VTCW_max p100s
                    p200s p300s p301s p400s p100_bcptime p200_bcptime
                    p300_bcptime p301_bcptime p400_bcptime

  **MSS**           MSSID MSS_Name Date_inDB Date_onSV Date_inITF VTCW_onSV
                    VTCW_inITF

  **SCtime**        SCT_Cycle SCT_VTCW SCT_Period Base_DT Real_DT Comment
                    MSS_Build MSSID

  **Snap_IDs**      Snapshot_ID Snapshot_Name Subsystem Num_Packets
                    Num_Bytes

  **Formats**       Format_ID Format_Name Num_Frames MSSID Initial_MSSID -
  ----------------- -------------------------------------------------------

Level 1 static data tables:

  --------------- -------------------------------------------------------
  **Table name**  Fields (in the order archived)

  **Mdcals**      TMID MSSID Units Type GAIN Min_DN C0 C1 C2 C3 C4 C5 C6
                  C7

  **TMavgid**     TMID MSSID

  **Tmcals**      TMID MSSID Units Type Min_DN C0 C1 C2 C3 C4 C5 C6 C7

  **Tmdecom**     TMID MSSID Format_ID

  **Tmderived**   DM_TMID MSSID Function_Name SM_TMID TMID1 TMID2 TMID3
                  TMID4 TMID5 TMID6 TMID7 Lag_Time CalvsRaw Lag_Time2
                  Lag_Time3 Lag_Time4 Lag_Time5 Lag_Time6 Lag_Time7
                  PostCvsR rate_mask

  **Tmlimits**    TMID MSSID Red_Low Red_High Yellow_Low Yellow_High
                  Display_Low Display_High

  **Tmnames**     TMID MSSID Initial_MSSID Subsystem Mnemonic Description
                  Datatype Start_Bit Length

  **Tmstates**    TMID MSSID Value State
  --------------- -------------------------------------------------------

Level 2 & 3 static data tables:

  ----------------- -------------------------------------------------------
  **Table name**    Fields (in the order archived)

  **orbit_times**   orbit_num orbit_start orbit_stop gs_valid_start
                    gs_valid_stop gs_capture saa_start saa_stop
                    eclipse_start eclipse_length notch_start notch_stop
                    notch_type orbit_quality comment

  **l2metadata**    pid shortname descrip outputfrom lowerbound upperbound
                    subsystem units

  **run_info**      run_id run_name run_date mod_date username comments T0
                    Tf VTcycle run_log prms_data

  **l3metadata**    id name descrip units
  ----------------- -------------------------------------------------------

#### File naming convention for dynamic data:

TABLENAME_cycle#\_StartYearDOY\[\_EndYearDOY\].cdf

where tablename corresponds to the chart of dynamic data tables,
following; cycle# refers to the spacecraft cycle number per the SCtime
data table; StartYearDOY is assumed to be midnight on the start of the
day of year in question (00:00:00.0); EndYearDOY is inclusive (up to
23:59:59.9) and is an optional parameter, in the case that the data
spans more than one day. If EndYearDOY is not included, that means that
only 24 hours of data are in the file (the 24 hours for StartYearDOY).
Note that DOY stands for Day of Year. There may be further file
descriptors for some data types, but these will be addressed further
with each data type and treated as an exception. It is possible that due
to the length of "TABLENAME" in each circumstance, the filename will be
longer than 32 characters total, but attempts have been made to keep
this circumstance to a minimum.

All dynamic and most static \*.cdf files are accompanied by a \*.sum
ASCII text file of the same prefix. This is a summary file, and it
discusses different metadata about the cdf file. For example, a typical
\*.sum file might include how many records were selected for a given cdf
file and the time range used.

Dynamic files are generally indexed by a spacecraft cycle and time
stamp. The concept of spacecraft cycle was necessary because a counter
"ticker" was needed to differentiate between, say, two vehicle tests
that had the same vehicle clock time. This is addressed more fully in
S0401. Each cycle number (integer) is detailed in the static SCtime data
file, along with specific comments. Dynamic data does not include cycle
number intrinsically; rather it is in the filename itself. For example,
a typical file name might be: events_12_2005149.cdf , where events would
indicate the Level 0 spacecraft event data, 12 would identify the cycle,
and 2005149 would be the year and day of year (24 hour period) for the
data.

Dynamic files include:

Level 0 dynamic data tables:

+--------------+-------------------------------------------------------+
| **Table      | Fields (in the order archived)                        |
| name**       |                                                       |
+--------------+-------------------------------------------------------+
| **Events**   | SCT_VTCW, Application, Event_Number                   |
+--------------+-------------------------------------------------------+
| **Packets**  | SCT_VTCW VCID Format_ID Frame_Counter Data            |
|              | \[Differentiated by SN/TM, whether or not Number of   |
|              | Frames=100, per Formats table\]                       |
|              |                                                       |
|              | \*\***Please note that "Packets" has been shortened   |
|              | to PKT in the filename**                              |
+--------------+-------------------------------------------------------+
| **DBROs**    | SCT_VTCW Packet_Number Source_Sequence Segment_Flag   |
|              | Data                                                  |
+--------------+-------------------------------------------------------+
| **MROs**     | APID SCT_VTCW Packet_Number Source_Sequence           |
|              | Start_Address Total_Length Segment_Address Data       |
+--------------+-------------------------------------------------------+
| *            | SCT_VTCW Counter Decimation Channel Axis Indx         |
| *Snapshots** | GSS_Spare Length Data \[indexed by Snapshot ID\]      |
+--------------+-------------------------------------------------------+
| **Tcor_fit** | First_ERT First_ERT_Microsecs Last_ERT                |
|              | Last_ERT_Microsecs C0 C1 Chisqr Station SF_Format_ID  |
+--------------+-------------------------------------------------------+
| **Tcor_Raw** | SCT_VTCW ERT ERT_Microsecs Station SF_Format_ID       |
+--------------+-------------------------------------------------------+

Level 1 dynamic data tables:

  ---------------- -------------------------------------------------------
  **Table name**   Fields (in the order archived)

  **Snanalog**     TMID, SCT_VTCW, Value

  **SNdiscrete**   These data types are covered by "Special Notes", below

  **Tmanalog**     These data types are covered by "Special Notes", below

  **Tmdiscrete**   These data types are covered by "Special Notes", below

  **Tmpseudo**     These data types are covered by "Special Notes", below

  **Tmaverage**    TMID, SCT_VTCW, Minimum_Value, Maximum_Value,
                   Average_Value, Std_Deviation, Value_Count

  **GPS_Timing**   SCT_VTCW SF_Frame_Count SQ_SciVehTime32 SQ_SciVehTime8
                   SQ_Sci10HzTime SQ_PPSv16F_Time

  **GPS_Orbit**    SCT_VTCW SF_Frame_Count SP_RecvrMode1 SP_GPS_WeekNum1
                   SP_GPSTimeWeek1 RP_ECEFPosX RP_ECEFPosY RP_ECEFPosZ
                   RP_ECEFVelX RP_ECEFVelY RP_ECEFVelZ SP_GPS_Digit_B
                   SP_GPS_Fract SP_Time_Trans
  ---------------- -------------------------------------------------------

Orbit Determination dynamic data tables

  ---------------- -------------------------------------------------------
  **Table name**   Fields (in the order archived)

  **Ephem**        year time xpos ypos zpos xvel yvel zvel \[referenced by
                   ID number contained in filename\]

  **Ephem_Info**   id description startyear starttime endyear endtime
                   datatype

  **Header**       id name value

  **Solution**     id label value

  **Covariance**   id row column value

  **Mean**         id year time instant i omega A B a phi
  ---------------- -------------------------------------------------------

Level 2 and Level 3 dynamic data tables:

  ----------------- -------------------------------------------------------
  **Table name**    Fields (in the order archived)

  **L2data**        pid run_id vtime pvalue (each run ID is stored, for the
                    mission, in its own file)

  **l2data_flag**   3 vtime last_updated GSvalid InSAA GPSdropout flag4
                    Gyro1_jump Gyro2_jump Gyro3_jump Gyro4_jump
                    Gyro1_oddres Gyro2_oddres Gyro3_oddres Gyro4_oddres
                    SQ1_ff SQ2_ff SQ3_ff SQ4_ff A115 A117 A121 A126 A129
                    A131 A140 A148 A149 A152 A156 Aflag1 Aflag2 Aflag3
                    Aflag4 AnyAnomaly

                    

  **L3data**        Id vt value (each run ID is stored, for the mission, in
                    its own file)
  ----------------- -------------------------------------------------------

Special notes on the Level 1 dynamic TM/SN tables:

Grouped as TMdata and SNdata, where TM data is 32K data rate, "full
resolution" data, and SN data is the 1K/2K TDRSS data (non-science).
Each of these data groups have a similar structure and the primary
difference between them is that since it had a faster telemetry rate, TM
data contains a lot more data points. TM data was used for science; SN
data was used only for health and safety.

The SN and TM data files are each grouped (respectively) by subsystem,
one week at a time. The file nomenclature is like the following example:

ECU_12_YYYYDOY_YYYYDOY\_\_TM.cdf where ECU represents the on-board
electronics subsystem (as detailed in the Tmnames table). 12 represents
the cycle number (12 was the cycle number for all IOC and science
mission data, as detailed in the SCtime table). The first YYYYDOY
represents the start year and day of year, and the second YYYYDOY
represents the end year and day of year for this data file. Note these
dates are inclusive and it is assumed that the day starts at 00:00:00.0
and ends at 23:59:59.9. The "TM" is for 32K data, and will be "SN" in
the case of 1K/2K data. .cdf represents the fact that these files are
using the NSSDC's "Common Data Format" for archival storage.

Each data file includes a header with the start and end time, and then
proceeds directly to the data for each TMID (mnemonic number) in the
subsystem.

  --------------- -------------------------------------------------------
  **Table name**  Fields (in the order archived)

  **TM/SNdata**   TMID #, a list of SCT_VTCW's, a list of corresponding
                  values. This pattern is repeated over and over for each
                  TMID in the subsystem.

                  If the TMID is a 'discrete' or 'Boolean' data type, its
                  value is saved as a 1- byte field, otherwise it is an 8
                  byte floating-point number.

  **Sndata**      Note that most SN data is saved as subsystem "ALL"
                  because it such a small data set by comparison
  --------------- -------------------------------------------------------

A sample TM/SN data file might look something like:

  ----------------------------------------------- -----------------------
  Standard NSSDC CDF header                       

  Cycle 12                                        

  Space Craft GPB                                 

  Start time (integer, vehicle time clock word)   

  Stop time (integer, vehicle time clock word)    

  TMID 1234 (See Tmnames for this mnemonic name)  

  ROWS 8 (# of rows for this TMID)                

  SCT_VTCW                                        VALUE

  2013456987                                      367.5

  2013456988                                      367.4

  2013456989                                      367.9

  2013456990                                      331.36

  2013456991                                      330.7145

  2013456992                                      370.1

  2013456993                                      335.77

  2013456994                                      372.4468

  TMID 1236                                       

  ROWS 5                                          

  SCT_VTCW                                        VALUE

  2013456987                                      0.043

  2013456988                                      0.5009

  2013456989                                      1.223

  2013456990                                      1.445

  2013456991                                      -1.568

  ...                                             ...

  ...                                             ...

  ...                                             ...

                                                  

  ET CETERA                                       
  ----------------------------------------------- -----------------------

The Tmpseudo data structure is identical to the above. The Tmaverage
data is similar in structure to the above, except that it contains more
columns, which include, as detailed above, Minimum_Value, Maximum_Value,
Average_Value, Std_Deviation, Value_Count.

## Documents

There is considerable documentation available for the Gravity Probe B
mission. This mission was one of the first to put all of its Acceptance
Data Packages online, and has scanned and digitized thousands of
drawings, papers and supporting documents. GP-B will work on a
best-effort basis to include as much of this material in the archive, in
common non-proprietary formats, as possible.

### Specifications

> Specifications include Stanford University documents and those from
> major subcontractor, Lockheed Martin Corporation. The document archive
> shall include all contract-deliverable documents from both agencies,
> and those documents shall be in PDF (Portable Document Format) format.

### Drawings

Drawings include Stanford University design drawings in creating the
science instrument assembly and supporting electronics, and design
drawings from Lockheed Martin for the space vehicle and its components.
These drawings were scanned from original printings and shall be in PDF
format.

### Test Documents/As-Run Procedures

> Test documentation and recorded test results shall be archived on a
> best-effort, as-available basis.

### Photographs

The Gravity Probe B mission has saved thousands of photographs and
created artwork as needed for the mission's Education & Public Outreach
department. The photographs mostly document the assembly of the science
instrument, its integration into the probe and then the dewar, final
spacecraft integration, several important pre-flight tests and the
necessary moves of the payload and vehicle, along with the launch. All
of these photographs will be archived in JPEG, GIF, or TIFF format,
though artwork may be archived in both Adobe proprietary format in one
of the common standard image formats to facilitate future use of the art
by others.

### Web Site

Upon conclusion of the Gravity Probe B mission, the mission web site
pages shall be transferred to the NSSDC for re-posting or archiving, at
their discretion.

# Schedule for Archive Generation, Validation, and Delivery. 

The principal archive elements, namely the science data products defined
in Section 5, will be generated following completion of the science data
collection period.

The timeline for archive delivery to NSSDC is shown in Table 6.1.  There
is one additional NSSDC data delivery date planned: approximately 70
gigabytes of Level 2 Data (April 2007). The final archive delivery may
include the 70 gigabyte subset data in its entirely if delivered as a
new version.

**Table 6.1 GP-B Archive Generation, Validation, and Release Schedule\
**

+------------------------+---------------------------------------------+
| Date                   |                Event                        |
+------------------------+---------------------------------------------+
| April 20, 2004         | Launch, On-orbit checkout                   |
+------------------------+---------------------------------------------+
| August 2004            | Science data collection                     |
+------------------------+---------------------------------------------+
| September 2005         | End of data collection                      |
+------------------------+---------------------------------------------+
| November 2005          | Draft MOU                                   |
+------------------------+---------------------------------------------+
| January 2006           | Final Draft MOU complete                    |
+------------------------+---------------------------------------------+
| February 2006          | Draft Archive Plan                          |
+------------------------+---------------------------------------------+
| October 2006           | Nominal end of mission                      |
+------------------------+---------------------------------------------+
| November 2006          | Delivery of ITAR sensitive documents on DVD |
+------------------------+---------------------------------------------+
| January 2007           | Final Draft Archive Plan complete           |
+------------------------+---------------------------------------------+
| April 2007             | Delivery of subset 70 GBytes Level 2        |
|                        | science data, delivered to NSSDC            |
+------------------------+---------------------------------------------+
| April 2007             | -   GP-B first results announcement         |
+------------------------+---------------------------------------------+
| June 2007              | -   Primary delivery of science data        |
+------------------------+---------------------------------------------+
|                        | -   Delivery of Mission Support Software    |
|                        |     LMCO database                           |
+------------------------+---------------------------------------------+
|                        | -   Delivery of pre-launch spacecraft test  |
|                        |     data                                    |
+------------------------+---------------------------------------------+
|                        | -   Delivery of spacecraft orbit ephemera   |
+------------------------+---------------------------------------------+
|                        | -   Delivery of GP-B web site snap shot     |
+------------------------+---------------------------------------------+
| December 2007          | Nominal end of no-cost extension            |
|                        |                                             |
|                        | -   Delivery of Level 3 data                |
+------------------------+---------------------------------------------+
| December 2007          | Delivery of any remaining SAO Guide Star    |
|                        | Data                                        |
+------------------------+---------------------------------------------+

# GP-B Data Release Policy. 

There are no proprietary data rights for the GP-B Mission data.
Uncalibrated data (Level 0 and Level 1) and reduced (Level 2) data will
be publicly released. Fully reduced, calibrated and corrected data
products (Levels 2 and 3) will be produced under the direction of the
science team for delivery to the NSSDC per the schedule given in table
6.1.

# Appendix A: Guide Star Data from the SAO

The Smithsonian Astrophysical Observatory (SAO) is a \"research
institute\" of the Smithsonian Institution. It is joined with the
Harvard College Observatory (HCO) to form the Harvard-Smithsonian Center
for Astrophysics (CfA).

## Guide Star data

Excerpted from <http://www.spaceref.com/news/viewpr.html?pid=13995> :

> "The \[GP-B\] satellite measurements have to be adjusted for at least
> one very significant astronomical effect. We \[at the CfA\] are using
> radio telescopes to measure the required adjustment,\" says
> Smithsonian radio astronomer Michael Ratner (CfA), who works with
> \[then-\]CfA Director Irwin Shapiro on the project.
>
> Gravity Probe B carries a telescope that focuses on a guide star \[IM
> Pegasi, also known as HR8703 and IM Peg\] in order to provide a
> reference point for measuring tiny deflections in the gyroscopes\'
> spin axes. The whole spacecraft is continually kept aligned to this
> star. Yet the star shifts its apparent position as both it and the Sun
> independently orbit the center of the Milky Way. As seen from the GP-B
> spacecraft, the apparent position of the guide star also is affected
> by the spacecraft\'s orbit around the Earth and the Earth\'s orbit
> around the Sun.
>
> To compensate for those effects, Shapiro and his colleagues have
> monitored the GP-B guide star for several years using a variety of
> radio telescopes. That monitoring will continue through the lifetime
> of Gravity Probe B. Only after all of the spacecraft data have been
> collected will the calculations be made that will test Einstein\'s
> theory.
>
> Previously Shapiro and Ratner observed IM Peg using the Hubble Space
> Telescope (HST). They have also recruited a team of optical
> astronomers to make other types of observations of this star.

Guide Star data is being organized and delivered to Gravity Probe B at
Stanford University by personnel currently or formerly at the Center for
Astrophysics, York University, University of California at Berkeley and
ETH Zurich. The time of archive-appropriate data delivery from CfA
personnel is still to be determined at the time of this writing. All of
the above personnel have agreed to package up relevant guide star data
using archival formats and including brief documentation. They will
provide that data to Gravity Probe B, so that GP-B can then provide the
data to the NSSDC. GP-B will ensure that CRC checks have been performed
on the data. The data is split into two categories: optical and radio
data observations.

### Optical Observations

The optical deliveries include images, astrometric, spectroscopic, and
photometric measurements and certain results derived from those
observations. Each data set will be accompanied by one or more
\"readme\" files which describes the data set, the instrument,
observations made, data content, data format, calibrations and/or data
reduction, information about data source and use, and a CRC32 checksum
for each file contained in the data set. 

Observations in the following list grouped under a single number will be
sent to Stanford University by a single astronomer who reduced or used
the group of observations.

The data to be archived include:

**1) AEOS, WIYN Speckle, and HST data** to be sent by Paul Hemenway
(CfA)**\
**\
The data to be archived for the three data sets will consist of data
reduced to a level useful in determining limits to the detectable
sources of background radiation around the GP-B guide star, IM Pegasi
(a.k.a. HR 8703, Hipparcos 112997, and HD 216489).   The Hubble Space
Telescope (HST) files are archived at the HST Space Telescope Science
Institute, and pointers will be given to those archives, in addition to
including the specific files used for GP-B analysis. Some specifics
about the individual data sets is given below:

> a\) AEOS adaptive optics images of IM Peg:
>
> \~11 FITS files\
> \
> b) WIYN speckle images of IM Peg:
>
> \~7 CDF format images\
> \
> c) HST multiband WFPC2 images of IM Peg and surrounding field:
>
> 30 FITS files of pipeline-calibrated a images
>
> 30 FITS files of the associated \"images\" containing the pixel flags
> for the pipeline-calibrated images
>
> Up to 14 FITS files of derived images used for GP-B studies

**2) Coronagraphic images made at the U. of Hawaii 2.2 m telescope** of
the IM Peg field in R band:

\~4 FITS images\
\
**3) Images made at the USNO Flagstaff Station** of IM Peg and the
surrounding field in B band:

> \~25 FITS images
>
> \~20 ASCII files of derived B magnitudes for background stars within
> or near the GP-B field of view

###### 4) To be sent by Stephen Marsden (University of Southern Queensland)

a)  Multiband photometry of IM Peg (and a check star) obtained at
    Fairborn Observatory and by Fairborn personnel:

> 18 ASCII files

b)  IM Peg spectra from Fairborn Observatory:

> \~700 ASCII files containing the calibrated spectra
>
> \~700 ASCII files containing the calibrated spectra with \"spliced
> orders\"
>
> c\) IM Peg spectra from the Anglo-Australia Telescope:
>
> 24 ASCII files
>
> d\) IM Peg spectra from the Crimean Astrophysical Observatory:
>
> 44 ASCII files
>
> e\) IM Peg spectra from Lick Observatory:
>
> 165 ASCII files
>
> f\) IM Peg spectra from Lick Observatory with photometric calibration:
>
> \~20 ASCII files
>
> g\) IM Peg spectra from the Nordic Optical Telescope:
>
> 142 ASCII files
>
> h\) The IM Peg spot maps computed at ETH Zurich from the above
> spectra:
>
> \~30 ASCII files containing the pixel values of the maps, spaced every
> \~25 days\
> \~30 PDF\'s displaying the above maps
>
> i\) Daily modeled IM Peg spectra computed at ETH Zurich from the above
> maps:
>
> 14 ASCII files, each containing spectra for 25 consecutive days
>
> j\) Mean angular offset between light centroid and primary disk
> center, computed at ETH Zurich, for each of the maps above:
>
> 1 ASCII file

## Radio Observations

Raw correlated VLBI data from VLBI observations of IM Peg and two or
three calibration sources conducted by the CfA and York University is
stored at the National Radio Astronomy Observatory archive (in FITS
files). The NRAO online archive contains the complete raw correlated
VLBI data from 1999 May 16 on
(<http://archive.nrao.edu/archive/e2earchive.jsp>). Earlier observations
are also available from the NRAO.

1)  York will deliver, in FITS format, the visibilities of the
    multi-source files for each of the 35 epochs between 1997 and 2005
    as well as the four earlier epochs between 1991 and 1994. Attached
    to these files are the calibration and flag tables. The data will be
    delivered in a "ready to process" format. In addition will be
    delivered ASCII files describing the contents of the data files.

2)  For each epoch there will be one to two gigabytes of data. Total
    estimated size of archived radio data: \~70 gigabytes.

# Appendix B: GP-B Acronyms

ACE Attitude Control Electronics

ACO Administrating Contracting Officer

ADP Acceptance Data Package

AGS GN station in Poker flats, Alaska

AIP Archival Information Package

AIPS Astrological Image processing system

AOS Acquisition of Signal

APID Application Process Identification

ATC Attitude & Translation Control Subsystem

BPS Bits Per Second

C&DH Command & Data Handling

CCCA Command/Control Computer Assembly

CCSDS Consultant Committee for Space Data Systems

CD Compact disc

CDR Critical Design Review

CDRL CDRL Contractor Data Requirements List

CfA Harvard-Smithsonian Center for Astrophysics

COBE Cosmic Background Explorer

CSTOL Colorado Spacecraft Test and Operations Language

DBRO Database Readout

DES Data Encryption Standard

DMA Detector Mount Assembly

DP Data Processing

DSN Deep Space Network

E&PO Education and Public Outreach

ECU Experiment Control Unit

EM Engineering Memo

EU Engineering Unit

FEP Front end processor

FFT Fast Fourier Transform

FSW Flight Software

GB Gigabyte

GMT Greenwich Mean Time

GN Ground network controlled by WFF

GP-B Gravity Probe B

GPS Global Positioning System

GSFC Goddard Space Flight Center

GSS Gyro Suspension System

GUI Graphical User Interface

HEPL Hansen Experimental Physics Labs at Stanford

HEX Hexadecimal

IOC Initial Operations Capability

IONet NASA\'s IP Operational Network

IPDU Internet Protocol Data Unit

kbps Kilobits per Second

LASP Laboratory for Atmosphere and Space Physics

LMMS Lockheed Martin Missiles & Space

MGS Mcmurdo Antarctica Ground Station

MB Megabyte

MOC Mission Operation Center

MRO Memory Readout- A type of data packet from the spacecraft

MSFC Marshall Space Flight Center

N/A Not Applicable

NIST National Institute of Standards & Technology

NOAA National Oceanic and Atmospheric Administration

NRAO National Radio Astrometric Observatory

NSSDC National Space Sciences Data Center

OASIS Operations and Science Instrument Support

OD Orbit Determination

PCB Program Control Board

POD Not an acronym, it's a cluster of computers

QA Quality Assurance

QUIKSCAT Quick Scatterometer, a NASA Earth satellite

REE Responsible Equipment Engineer

R/O Readout

RTworks Real-Time monitoring, display, logging & cntrl s/w by Talarian
Corp

SAA South Atlantic Anomaly

S/C Spacecraft

SN Space Network (TDRSS)

S/V Space Vehicle

SWSI SN Web Service Interface

SADM Solar Array Deployment Mechanism

SAFS Standard Autonomous File Server

SAO Smithsonian Astrophysical Observatory

SGI Silicon Graphics, Inc.

SIM Simulation

SIA Science Instrument Assembly

SLR Satellite Laser Ranging

SQUID Superconducting Quantum Interference Device

SSR Solid State Recorder

STK Satellite Tool Kit

SU Stanford University

Sybase Relational Data Base Management Software

TBD To Be Determined

TCAD Telemetry Checking, Analysis and Display

TDP Telemetry Data Processing Software

TDRSS Tracking and Data Relay Satellite System

TQSM Telemetry Quality and Status Monitoring

TRE Telescope Readout Electronics

UT Universal time

VAFB Vandenberg Air Force Base

VLBI Very Long Baseline Interferometry

WFF Wallops Flight Facility

WGS Wallops Ground Station (Wallops island)

WSC White Sands Complex (TDRSS)

WOTIS Wallops Orbital Tracking Information System

#  

# Appendix C: ITAR

The U.S. State Department\'s International Traffic in Arms Regulations
(ITAR) classifies spacecraft systems and scientific satellites \-- and
all related data, components, software, parts and material \-- as
\"significant military equipment\" subject to tight control. ITAR bars
the disclosure of unclassified technical data by American companies or
universities to foreign students, faculty and collaborators if they are
from countries listed as \"sensitive\" or \"terrorist exporting.\"

The Gravity Probe B spacecraft and instrument fell under ITAR
restriction in late 1999, more than 35 years after the project's
inception. Anything considered public knowledge about Gravity Probe B
before its re-classification (e.g. published papers, newspaper
articles), remains outside the ITAR restriction. However, some internal
publications and schematics are considered ITAR restricted as determined
by the U.S. State Department Statute.

Gravity Probe B, and their major subcontractor, Lockheed Martin
Corporation, has made a considerable effort to classify all documents
and schematics appropriately.

The NSSDC is the final entity responsible for distribution of Gravity
Probe B data and its supporting materials (including internal
publications and schematics).  The NSSDC has agreed to seek
re-classification of ITAR restricted materials, and to make available
ITAR cleared material as appropriate.