**National Aeronautics and Space Administration**

**Goddard Space Flight Center**

**Project Data Management Plan**

**for the IMAGE Mission**

[James L. Green \_\_\_\_\_4/8/97]{.underline}

Prepared by: Dr. James L. Green Date

IMAGE Co-Investigator

[James Burch \_\_\_April 1997]{.underline}

Concurrence: Dr. James L. Burch (SwRI) Date

IMAGE Principal Investigator

[Thomas Moore \_\_\_ April 1997]{.underline}

Concurrence: Dr. Thomas E. Moore Date

IMAGE Mission Scientist

[Frank Volpe May 1997]{.underline}

Concurrence: Mr. Frank Volpe (410) Date

IMAGE Mission Manager

[Bill Worrall \_\_\_ May 1997]{.underline}

Concurrence: Mr. William D. Worrall (630.1) Date

Manager, Orbiting Satellites Project

[Joseph King \_\_\_ May 1997]{.underline}

Concurrence: Dr. Joseph H. King (633) Date

Head, National Space Science Data Center

[Robert Carovillano \_\_\_June 1997]{.underline}

Concurrence: Dr. Robert L. Carovillano Date

IMAGE Program Scientist

TABLE OF CONTENTS

1.0 Introduction 1

1.1 Purpose and Scope 1

1.2 PDMP Development, Maintenance, and Management Responsibility 1

2.0 Project Overview 1

2.1 Science Objectives 2

2.2 Data Acquisition and Access Overview 2

2.3 Summary of Mission Operations 2

3.0 Science Instrumentation 3

3.1 Neutral Atom Imaging (NAI) Instrument Performance Requirements 4

3.1.1 Low Energy Neutral Atom \[LENA\] Imager 5

3.1.2 Medium Energy Neutral Atom \[MENA\] Imager 6

3.1.3 High Energy Neutral Atom (HENA) Imager 6

3.2 Photon Imagers 6

3.2.1 He+ 30.4 nm Imager (EUV) 7

3.2.2 Far Ultraviolet Imagers (FUV) 7

3.3 Radio Plasma Imager (RPI) 9

4.0 IMAGE End-to-End Data Flow 9

4.1 Overview 10

4.2 Science and Missions Operations Center 10

4.3 Data Products and Access Overview 10

4.3.1 Level-0 Data 11

4.3.2 Level-1 Data 11

4.3.3 Level-2 and Higher Level Data Products 12

4.3.4 Attitude and Orbit Products 12

4.4 Data Archiving and Distribution 12

4.5 Archival Data Volume 12

4.6 Archive Data Access 13

5.0 Data Rights and Rules for Data Use 15

6.0 References 15

Acknowledgments 15

Appendix A- Acronym List 16

**1.0 Introduction**

This document describes the Project Data Management Plan (PDMP) for the
Imager for Magnetopause-to-Aurora (IMAGE) mission. IMAGE is NASA\'s
first medium-sized Explorer mission (or MIDEX) whose development cost
cap for payload and spacecraft is approximately \$68 million dollars
(FY94). IMAGE also has a mission operations and data analysis cost cap
of \$15 million dollars (FY94). The IMAGE PDMP is designed to be
consistent with the IMAGE Level-1 Requirements Definition document.

1.1 Purpose and Scope

This data management plan describes the generation and delivery of IMAGE
science data products, institutional responsibilities for data analysis,
and the transfer of archival data products to the National Space Science
Data Center (NSSDC). Covered in this plan are:

> 1\. Brief description of the instruments
>
> 2\. Description of the data flow
>
> 3\. Description of the science data products
>
> 4\. Processing requirements and facilities
>
> 5\. Policies for access and use of IMAGE data
>
> 6\. Data product documentation

It is important to note that the IMAGE mission support two data
telemetry streams; a science data stream (full resolution data stored
and forwarded on command) and a continuous low bit rate (\~500 b/s)
real-time data link. The real-time data link will be used by NOAA in
their Space Evironment Center (SEC) for space weather analysis and
alerts. The management of the data from the IMAGE real-time data link
will not be covered in this plan. At this time most of the details of
that link have not been defined and are the responsibility of NOAA.

1.2 PDMP Development, Maintenance, and Management Responsibility

The IMAGE Project Office at Goddard Space Flight Center (GSFC), Code
410, is responsible for the development, maintenance, and management of
the PDMP until IMAGE has transitioned to an operational mission after
launch. Responsibility for the plan remains with the IMAGE Mission
Manager, Mr. Frank Volpe until 30 days after launch. After signature
release and until transition to an operational mission, the IMAGE PDMP
will be modified and updated as required in accordance with the
Configuration Management Plan for Midex Missions.

After launch and instrument check the responsibility for the IMAGE
mission will be transistioned to the Orbiting Satellites Project (OSP,
Code 630.1) within the Space Sciences Directorate. The responsibility
for the IMAGE PDMP will also transition to OSP.

**2.0 Project Overview**

The IMAGE mission was selected as a result of AO-95-OSS-02 for MIDEX
missions. The Phase B study began on May 10, 1996, and the Mission
Confirmation Review was held on February 25-27, 1997. Mission
Confirmation was granted on March 31, 1997. The IMAGE mission is
scheduled to be launched in January 2000.

2.1 Science Objectives

The overall science objective of IMAGE is to determe the global response
of the magnetosphere to changing conditions in the solar wind. Three
fundamental questions which must be addressed by IMAGE to accomplish its
primary objective are:

> What is the mechanism for injecting plasma into the magnetosphere on
> substorm and magnetic storm time scales?
>
> What is the directly driven response of the magnetosphere to solar
> wind changes?
>
> How and where are magnetospheric plasmas energized, transported, and
> subsequently lost during storms and substorms?

IMAGE will address these objectives in unique ways using neutral atom
imaging (NAI) over an energy range from 10 eV to 200 keV, far
ultraviolet imaging (FUV) from 121 to 190 nm, extreme ultraviolet
imaging (EUV) at 30.4 nm, and radio plasma imaging (RPI) over the
density range from 0.1 to 105 cm-3 throughout the magnetosphere.

2.2 Data Acquisition and Access Overview

The IMAGE mission will operate with a near 100% duty cycle with all
instruments in their baseline operational modes. The IMAGE Level-0 data
will be processed into Level-1 data (Browse Products) within 24 hours
after their receipt in the Science and Mission Operations Control Center
(SMOC) at GSFC. These data products will be transferred to the NSSDC and
posted immediately on the world wide web for use by the international
community of scientists and the public. Level-2 data products will be
posted on the web and at NSSDC as they are generated.

+-------------------------------------+--------------------------------+
| **Orbit Description**               | inclination: 90˚               |
|                                     |                                |
|                                     | apogee: 44,590 km              |
|                                     |                                |
|                                     | perigee: 1000 km               |
|                                     |                                |
|                                     | period: 13.5 hr.               |
+-------------------------------------+--------------------------------+
| **Launch Date**                     | 1 January 2000                 |
+-------------------------------------+--------------------------------+
| **Launch Vehicle**                  | Delta 7326-9.5                 |
+-------------------------------------+--------------------------------+
| **Nominal Mission Duration**        | 2 years                        |
+-------------------------------------+--------------------------------+
| **Potential Mission Life**          | 5 years                        |
+-------------------------------------+--------------------------------+
| **Spacecraft Mass**                 | \~500 kg                       |
+-------------------------------------+--------------------------------+
| **Spin Rate**                       | 0.5 rpm                        |
+-------------------------------------+--------------------------------+
| **Attitude Control Accuracy**       | spin axis: 0.1˚                |
|                                     |                                |
|                                     | spin phase: 0.1˚               |
+-------------------------------------+--------------------------------+
| **On-Board Data Storage Capacity**  | 2 GB                           |
+-------------------------------------+--------------------------------+
| **Continuous Data Acquisition       | 2.5 Mbits/sec                  |
| Rate**                              |                                |
+-------------------------------------+--------------------------------+

**Table 2.1**; IMAGE Mission Summary

2.3 Summary of Mission Operations

The IMAGE mission summary is shown in Table 2.1. After launch and
initial activation of the IMAGE spacecraft systems, the attitude
determination and control system (ADAC) will orient the spacecraft spin
axis perpendicular to the orbit plane to within 1˚. The ADAC will
maintain a spin rate of at least 0.5 rpm while deploying the four RPI
radial wire antennas (x and y axis). After full extension of the x and y
axis antennas, the spacecraft will deploy the two axial (z axis)
antennas. The full deployment for all of the RPI antennas should take
approximately 30 days. After

completion of the antenna deployment the IMAGE spacecraft will be spin
stabilized (\~0.5 rpm) in an 90˚ inclination orbit of approximately 1000
km perigee by 7 Earth radii (RE) apogee.

The orbital evolution over the two-year mission life is illustrated in
Fig. 2.1. The spacecraft will operate in a store-and-forward mode with
data downlinks of 30 minutes once per orbit to the Deep Space Network
(DSN). Command uplinks are planned for once per week.

![](media/image1.pct){width="705.0in" height="158.0in"}

**Fig. 2.1** IMAGE orbital evolution

**3.0 Science Instrumentation**

The science payload for IMAGE consists of instrumentation for obtaining
images of plasma regions in the Earth\'s magnetosphere. The four types
of imaging techniques used by IMAGE are: neutral atom imaging (NAI), far
ultraviolet imaging (FUV), extreme ultraviolet imaging (EUV), and radio
plasma imaging (RPI). There are 3 instruments used in making NAI
measurements. These instruments are: the Low Energy Neutral Atom (LENA)
imager, the Medium Neutral Atom (MENA), and the High Energy Neutral Atom
(HENA) imager. Each of these instruments cover specific energy ranges
and utilize a variety of different instrument technologies. There are 3
instruments utilizing photons for imaging. These instruments are: the
Extreme Ultraviolet (EUV), three instruments in the Far Ultraviolet
(FUV) frequency range (the Spectrographic Imager (SI), Wideband Imaging
Camera (WIC), the Geocoronal (GEO) imager). Finally, very long
wavelength remote sounding will be accomplished with the Radio Plasma
Imager (RPI). As proposed, the performance requirements for these IMAGE
instruments are listed in Table 3.1 below. It is important to note that
nearly all the IMAGE instruments will exceed these requirements.

The minimum time resolution for images from all instruments, except the
RPI, is the spacecraft spin period of two minutes. The RPI will have
modes which will allow density profile determination on a time scale as
short as 1 minute and radio \"skymaps\" or images at specific
frequencies in seconds. For the other instruments, images can be
constructed from data taken over multiple spin periods. The IMAGE
Science Team will have the responsibility to generate and validate the
data products but claim no proprietary data rights to any of the data.

+-----+----------------+----------------------------------------------+
| Im  | Measurement    | Critical Measurement Requirements            |
| age |                |                                              |
+-----+----------------+----------------------------------------------+
| *   | Neutral atom   | *FOV:* 90° (image ring current at apogee).   |
| *NA | composi­tion    |                                              |
| I** | and            | *Angular Resolution:* 8° x 8°                |
|     | e              |                                              |
|     | nergy-resolved | *Energy Resolution (E/E):* 0.8               |
|     | images over    |                                              |
|     | three energy   | *Composition:* distinguish H and O in        |
|     | ranges:        | magnetospheric and ionospheric sources,      |
|     |                | interstellar neutrals and solar wind.        |
|     | 10-300 eV      |                                              |
|     | (LENA)         | *Image Time:* 4 minutes (resolve substorm    |
|     |                | development).                                |
|     | 1-30 keV       |                                              |
|     | (MENA)         | *Sensitivity:* effective area 1 cm2 for each |
|     |                | sensor.                                      |
|     | 10-200 keV     |                                              |
|     | (HENA)         |                                              |
+-----+----------------+----------------------------------------------+
| *   | 30.4 nm        | *FOV:* 90° (image plasmasphere from apogee). |
| *EU | imaging of     |                                              |
| V** | plasmasphere   | *Spatial Resolution:* 0.1 Earth radius from  |
|     | He+ column     | apogee.                                      |
|     | densities.     |                                              |
|     |                | *Image Time:* several minutes to hours       |
|     |                | (resolve plasmaspheric processes).           |
+-----+----------------+----------------------------------------------+
| *   | Far            | *FOV:* 16° for aurora (image full Earth from |
| *FU | ultraviolet    | apogee), 60° for geocorona.                  |
| V** | imaging of the |                                              |
|     | geocorona at   | *Spatial Resolution:* 70 km (WIC),90 km (SI) |
|     | 121.6 nm (GEO) |                                              |
|     | and the aurora | *Spectral Resolution:* separate cold         |
|     | at 140-190 nm  | geocorona H from hot proton precipitation    |
|     | (WIC) and      | (l\~0.2 nm near 121.6 nm); reject 130.4 nm   |
|     | 121.6 and      | and select 135.6 nm electron aurora          |
|     | 135.6 nm (SI)  | emissions.                                   |
|     |                |                                              |
|     |                | *Image Time:* 2 minutes (resolve auroral     |
|     |                | activity).                                   |
+-----+----------------+----------------------------------------------+
| *   | Remote sensing | *Density range:* 0.1-105 cm-3 (determine     |
| *RP | of electron    | electron density from inner plasmasphere to  |
| I** | densities and  | magnetopause).                               |
|     | magnetospheric |                                              |
|     | boundary       | *Spatial resolution:* 500 km (resolve        |
|     | locations      | density structures at the magnetopause and   |
|     | using radio    | plasmapause).                                |
|     | sounding.      |                                              |
|     |                | *Image Time:* 1 minute (resolve changes in   |
|     |                | boundary locations).                         |
+-----+----------------+----------------------------------------------+

Table 3.1; Instrumentation Required to Meet Science Objectives

3.1 Neutral Atom Imaging (NAI) Instrument Performance Requirements

The science requirements driving the NAI instrumentation for IMAGE are
(1) to image the inner magnetosphere including the ring current on a
time scale of 300 seconds and (2) to resolve the major species
contributing to neutral atom fluxes. To meet these requirements a suite
of three NAI instruments will provide angle, energy, and
composition-resolved images at energies from 10 eV to 500 keV.

IMAGE will carry three NAI instruments because of the different
techniques that apply to low (0.01 to 0.5 keV), medium (1 to 30 keV),
and high (10 to 500 keV) neutral atoms. The detailed instrument
performance requirements for the NAI instruments are shown in Table 3.2.

Angular information is obtained over 90˚ fans with angular resolution
between 4˚ x 4˚ and 8˚ x 8˚ depending on species and energy. Spacecraft
spin is used to obtain angular information in the orthogonal (azimuthal)
direction. All three instruments have collimators that consist of
serrated, blackened surfaces to reduce internal scattering. The
collimators contain deflection potentials of 10 kV that deflect and
absorb charged particles below 100 keV/e. Small broom magnets remove
electrons with energies \<200 keV.

+--------------------------+---------------+-------------+------------+
|                          | LENA          | MENA        | HENA       |
+--------------------------+---------------+-------------+------------+
| **Energy range \[keV\]** | 0.01 - 0.3    | 1-30        | 10-500     |
+--------------------------+---------------+-------------+------------+
| **Energy resolution      | 0.8           | 0.8         | 3 kev      |
| \[E/E\]**                |               |             |            |
+--------------------------+---------------+-------------+------------+
| **Instantaneous FOV      | 8 x 90        | 4 x 107     | 90 x 120   |
| \[deg\]**                |               |             |            |
+--------------------------+---------------+-------------+------------+
| **Total FOV \[deg\]**    | 90 x 360      | 107 x 360   | 120 x 360  |
+--------------------------+---------------+-------------+------------+
| **Pixel resolution       | 88            | 48          | 44         |
| \[deg\]**                |               |             |            |
+--------------------------+---------------+-------------+------------+
| **Geometric factor       | 0.2           | 0.07        | 1.6        |
| \[cm2sr\]**              |               |             |            |
+--------------------------+---------------+-------------+------------+
| **Pixel sensitivity**    | 7x10-4        | 4x10-3      | 4.5x10-3   |
|                          |               |             |            |
| **\[cts/atom cm2sr       |               |             |            |
| eV/eV\]**                |               |             |            |
+--------------------------+---------------+-------------+------------+
| **Image time \[s\]**     | 120           | 120         | 120        |
+--------------------------+---------------+-------------+------------+
| **Pixel array            | 2M4E11A       | 2M16E 32A   | 4M16E32A   |
| dimensions**             |               |             |            |
+--------------------------+---------------+-------------+------------+
| **UV rejection**         | 10-7          | 10-7        | 10-9       |
+--------------------------+---------------+-------------+------------+
| **Electron rejection**   | 10-10         | 10-5        | 10-5       |
+--------------------------+---------------+-------------+------------+
| **Ion rejection**        | 10-8          | 10-5        | 10-5       |
+--------------------------+---------------+-------------+------------+

**Table 3.2** NAI Instrument Performance Parameters

3.1.1 Low Energy Neutral Atom \[LENA\] Imager

LENA \[*Ghielmetti et al*., 1994\] combines standard plasma analyzer
techniques with cesiated neutral-to-negative-ion surface conversion
technology to measure composition and energy spectra of neutral atoms
(H, D, 3He, 4He, and O) at 10--500 eV. LENA consists of a collimator,
conversion unit, extraction lens and acceleration region, dispersive
electrostatic energy analyzer, and time-of-flight (TOF) mass analyzer
with position-sensitive particle detection. Particles enter the
instrument through a collimator with elevation acceptance defined by the
height of the collimator. Neutrals are converted to negative ions
through near specular reflection from a low-work-function cesiated
tungsten conversion surface \[*Wurz et al*., 1995\]. The surface is
segmented to cover a 90˚ azimuthal acceptance.

Beyond the conversion surface, LENA is an ion mass spectrograph.
Neutrals converted to negative ions at the Cs surface are accelerated
away from the conversion surface and measured by a spherical
electrostatic analyzer. The electrostatic analyzer is dispersive in
energy and focusing in elevation angle.

The three main sources of instrument background for LENA are UV photons,
photoelectrons from the conversion surface, and negative ions produced
by attachment of photoelectrons to residual gas molecules. UV photons
scattered at near specular angles from the conversion surface enter a
light trap at the back, while the electrostatic analyzer provides
further multiple bounce rejection. Photoelectrons from the conversion
surface are separated from the negative ions and diverted into a trap by
a weak magnetic field between a small magnet at the back of the
conversion surface and another at the dispenser. This magnetic field
also traps electrons scattered through the collimator. Ion background
from residual gas is minimized by accelerating photoelectrons away from
the sensitive region. Any negative ions that are thereby produced will
be discriminated against by their lower energies relative to those
produced on the surface.

LENA has one operation mode and one surface regeneration mode. In a
typical orbit, the shutter will open after a perigee pass, and
low-energy neutral atom imaging will proceed throughout the orbit until
near perigee, when the shutter will close again. Approximately every 10
days the instrument will be cycled autonomously through the conversion
surface regeneration mode.

3.1.2 Medium Energy Neutral Atom \[MENA\] Imager

The MENA imager is a slit camera with straight-through optics, which
samples and resolves simultaneously all velocities, all polar angles
within a 107˚ fan, and all masses. This spectrographic feature is very
important for magnetospheric imaging because the weak fluxes of neutral
atoms require the instrument to have a high duty cycle.

The MENA analyzer consists of a collimator, UV rejection grating, start
foil, position-sensitive anode, TOF analyzer, and pulse-height analyzer.
The collimator plates use electrostatic deflection to reduce charged
particle background. The other significant background that must be
eliminated is ultraviolet light from the Sun and geocorona. The UV
grating acts as a wave guide to reduce the Lyman Alpha UV fluxes by a
fraction of 10-4. The grating also reduces the neutral atom flux by 90%.
Velocity analysis (through TOF measurements made with the start/stop
MCP), combined with pulse-height analysis, yields mass resolution
sufficient to separate H and O.

3.1.3 High Energy Neutral Atom (HENA) Imager

HENA is a slit camera with a 90˚ x 120˚ field of view and a segmented
focal plane incorporating an imaging solid-state detector (SSD) array in
one portion and an MCP with position-sensitive anode in the other. Pulse
height analysis of the SSD pulses provides total energy, which, combined
with the TOF velocity determination, yields neutral atom mass. The MCP
pulses are also pulse-height analyzed, yielding sufficient separation of
H and O. Each pixel is viewed both by the SSD array and the MCP as the
scene is scanned. HENA acquires angular images by locating the start
pulses on the entrance slit and the stop pulses in the image plane. The
collimator serves to suppress charged particle entry by biasing adjacent
collimating plates at ± 10 kV.

The UV background is suppressed by a combination of (1) a C-Si foil that
reduces the UV flux, (2) the insensitivity of the SSD to UV photons, and
(3) a triple-coincidence system for the MCPs in which start and stop
pulses must fall within valid time windows, and a second stop from the
back of a foil placed directly over the stop MCP is collected by the
coincidience stop MCP.

All HENA potentials are static except for infrequent adjustments of MCP
gain. After activation and checkout, HENA runs in a single operational
mode. Some choices of data product priorities can be made as software
options, providing, for example, a periodic (e.g., monthly) calibration
mode to check the TOF/PH identification of atomic species, the
pulse-amplifier chains, and the binning logic.

3.2 Photon Imagers

There are three photon imagers required by IMAGE. The EUV instrument
images resonantly scattered solar emissions from plasmaspheric He+ at
30.4 nm. Two FUV instruments, SI (Spectrographic Imager) and WIC
(Wideband Imaging Camera) image the Earth's electron and proton auroral
emissions. A Geocorona Oxygen Cell (GEO), which is part of SI, images
the hydrogen geocorona. General characteristics of the imagers are
listed in Table 3.3 below.

<table>
<colgroup>
<col style="width: 7%" />
<col style="width: 13%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 6%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 8%" />
<col style="width: 7%" />
<col style="width: 10%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Inst.</strong></td>
<td><strong>Measurement Type</strong></td>
<td><strong>Focal Length (mm)</strong></td>
<td><strong>Aper-ture (mm2)</strong></td>
<td><strong>(nm)</strong></td>
<td><strong>Res. (nm)</strong></td>
<td><p><strong>Instant. FOV</strong></p>
<p><strong>(deg)</strong></p></td>
<td><p><strong>Tot.</strong></p>
<p><strong>FOV (deg)</strong></p></td>
<td><strong>Pixel FOV (deg)</strong></td>
<td><p><strong>Sensi-tivity (c/R/</strong></p>
<p><strong>pixel)</strong></p></td>
<td><strong>Time Res. (min)</strong></td>
<td><p><strong>Spatial Res.</strong></p>
<p><strong>@7RE (km/pix)</strong></p></td>
</tr>
<tr class="even">
<td><strong>EUV</strong></td>
<td>Plasmaspheric He+ 30.4 nm</td>
<td>75</td>
<td><p>25</p>
<p>( 3)</p></td>
<td>30.4</td>
<td>5.0</td>
<td>30 x 90</td>
<td><p>90x</p>
<p>360</p></td>
<td>0.5 x 0.5</td>
<td>2.4</td>
<td>2</td>
<td>640 x 640</td>
</tr>
<tr class="odd">
<td><strong>FUV/SI</strong></td>
<td>Auroral LBH (narrow band), Lyman-</td>
<td>68</td>
<td>112</td>
<td><p>121.8&amp;</p>
<p>135.6</p></td>
<td><p>0.2</p>
<p>&amp;</p>
<p>3</p></td>
<td>1515</td>
<td>15x360</td>
<td>0.11</td>
<td>0.05</td>
<td>2</td>
<td>90 x 90</td>
</tr>
<tr class="even">
<td><strong>FUV/GEO</strong></td>
<td><p>Geocoronal</p>
<p>Lyman -</p></td>
<td>60</td>
<td>132</td>
<td>121.6</td>
<td>0.2</td>
<td><p>1x1</p>
<p>(3 cells)</p></td>
<td><p>60x</p>
<p>360</p></td>
<td>1</td>
<td>0.1</td>
<td>2</td>
<td>N/A</td>
</tr>
<tr class="odd">
<td><strong>FUV/WIC</strong></td>
<td>Auroral LBH (broad band)</td>
<td>22.4</td>
<td>60.8</td>
<td>140–190</td>
<td>N/A</td>
<td>30x22.5</td>
<td><p>22.5x</p>
<p>360</p></td>
<td>0.09</td>
<td>0.1</td>
<td>2</td>
<td>70x70</td>
</tr>
</tbody>
</table>

Table 3.3; Photon Imager Instrument Performance Parameters

3.2.1 He+ 30.4 nm Imager (EUV)

Effective imaging of plasmaspheric He+ requires global "snapshots" in
which the high apogee of the IMAGE mission and the wide FOV of the EUV
imager provide, in a single exposure, a map of the entire plasmasphere
from the outside with a sensitivity of 0.2 count/s-pixel-Rayleigh (R), a
spatial resolution of 0.1 RE, and a time resolution of several minutes.
The 30.4-nm feature is easy to measure because it is the brightest ion
emission from the plasmasphere, it is spectrally isolated, and the
background is negligible. Measurements are easy to interpret because the
plasmaspheric He+ emission is optically thin, so its brightness is
directly proportional to the He+ column abundance.

EUV consists of three identical sensor heads serviced by a common
electronics module. It employs elements of new technology, multilayer
mirrors. Because it is simple and lacks moving parts, the EUV is rugged
and reliable. Each sensor head has a field of view of 30˚ x 30˚. The
three sensors are tilted relative to one another to cover a fan-shaped
instantaneous FOV of 90˚ x 30˚. As the satellite spins, the fan sweeps a
90˚ x 360˚ swath across the sky.

Each EUV sensor achieves high throughput and a wide field of view by
using a large entrance aperture and a single spherical mirror. A
multilayer reflective coating on the mirror selects a narrow 5-nm
passband around the 30.4 nm line. To circumvent the red leak in the
multilayer mirror, the filter blocks H Lyman, a contamination from the
geocorona. The detector consists of two curved, tandem MCPs with an
alkali halide front surface photocathode. The detector's spherical input
surface minimizes the effects of spherical aberration. Readout from the
detector is from a 128 x 128 wedge and strip anode. The sensitivity
(accounting for the duty cycle inherent in a spinning spacecraft) is 0.2
count/(sec pixel) per R, where the pixel size is taken to be 0.1 RE. By
summing pixels to make a spatial resolution element (called a *resel*)
of 0.5 RE, the count rate is 5 counts/(sec resel) per R.

3.2.2 Far Ultraviolet Imagers (FUV)

Science requirements driving FUV imager designs are (1) to image the
entire auroral oval from a spinning spacecraft at 7 RE apogee altitude,
(2) to separate spectrally the hot proton precipitation from the
statistical noise of the intense, cold geocorona, and (3) to separate
spectrally the electron and proton auroras. FUV consists of two imagers
that combine high spectral discrimination, high spatial resolution, and
the greatest possible sensitivity to meet these requirements.

In the FUV range up to \~160 nm, there are several bright auroral
emission features that compete with the dayglow emissions. For the
electron aurora, the brightest is 130.4 nm OI, which is multiply
scattered in the atmosphere and thus cannot be used for auroral
morphology studies. The next brightest is the 135.6 nm OI emission\].
Separation of the 130.4 and 135.6 nm lines necessitates the use of a
spectrometer because even reflective narrow-band filter technology
cannot satisfy the \~3 nm wavelength resolution requirement. Above 135.6
nm, weak LBH lines can be detected using narrow-band filter technology.
Separate imaging of the intense, cold geocorona (Lyman emissions at
121.6 nm) and the less intense, Doppler-shifted Lyman auroral emissions
requires significantly higher spectral resolution (0.2 nm).

**Spectrographic Imager (SI).** The relatively high wavelength
resolution requirement is satisfied by the SI. The 0.2-nm wavelength
resolution drives the size of the instrument and consequently the number
of mirrors in the optics system. Also the narrowness of the slits in the
spectrometer limit the dwell time during which a pixel is in the field
of view.

The SI is a Wadsworth spectrometer, which uses a diffraction grating to
produce separate images of 135.6 nm emissions from the electron aurora
and 121.8 - 122.2 nm doppler-shifted Lyman emissions from the proton
aurora. The 130.4 nm oxygen airglow emission and the geocorona 121.6
Lyman emission are blocked out. The detectors use a KBr photocathode on
a MgF2 window image tube with MCP intensification. The intensified image
is detected by a crossed delay-line type detector with two 32 x 128
pixel active areas. Added to the SI is a Geocorona Oxygen Cell (GEO),
which provides three 1˚ narrow-band photometer channels of geocorona
data at 121.6 nm.

The SI has only one mode of operation. For some orientations of the spin
axis, the Sun may enter the field of view of SI at some spin phases. As
with EUV, the control microprocessor will automatically reduce the high
voltage to the MCPs to avoid excessive counting rates. The filters will
prevent damage to the detector by focused visible sunlight.

**Wideband imaging camera (WIC).** The relatively high sensitivity
requirement for auroral imaging is satisfied by the WIC. This imaging
camera uses the basic design flown on the Freja and Viking \[*Auger et.
al*, 1987\] satellites to measure the auroral LBH emissions in a
relatively broad band from 140 nm to 190 nm. The large field of view
permits a long dwell (or integration) period and increases the apparent
sensitivity.

The WIC optics design is identical to that of the Freja camera. Incident
photons pass through a filter that blocks the Lyman emissions and
protects the detector from direct, focused sunlight. The primary and
secondary mirrors have a coating that is highly reflective (\>60%) in
the FUV but has minimum (\<3%) reflectance out of band. MCPs are used to
intensify the image, which is produced on a phosphor and fiber-optically
coupled to a diode array.

Operation of the WIC is essentially identical to that of SI. Readout
occurs once per 0.1˚ of rotation for a frame rate of 30 frames/s at 0.5
rpm. The camera data are digitized and co-added in memory and the
addresses are selected according to the rotational phase of the
spacecraft. This technique minimizes the distortion correction required
by the imager.

3.3 Radio Plasma Imager (RPI)

The Radio Plasma Imager (RPI) is a transmitter/receiver system that
responds to the science requirement for the continuous remote sensing of
plasma densities, structures and dynamics in the magnetosphere and
plasmasphere. The instrument measures the time delay, angle-of-arrival,
and Doppler shift of magnetospheric echoes over the frequency band from
3 kHz to 3 MHz. This frequency range makes possible remote sensing of
plasma densities from 0.1 to 105 cm-3. The performance parameters for
the RPI to meet science objectives are listed in Table 3.4 and Table 3.5
below. Programmable operational modes selected within the limits listed
in Tables 3.4 and 3.5 will focus on specific magnetospheric and
plasmaspheric features.

  ---------------------- ------------------------- ---------------------------
  Measurement            Nominal Resolution        Limits

  **Echo Range**         500 km                    0.1 to 5 RE

  **Angle-of-Arrival**   1˚ at 40 dB S/N           resolution = 2/\[S/N\]

  **Doppler**            0.125 Hz                  75 Hz

  **Time**               8 seconds/frequency       4 seconds/frequency
  ---------------------- ------------------------- ---------------------------

Table 3.4 RPI Measurement Performance Parameters

  ------------------ ------------------------- ---------------------------
  Parameter          Nominal                   Limits

  **RF Power**       10 W                      10 W

  **Pulse Width**    53 msec                   3.2 to 125 ms

  **Receiver         300 Hz                    fixed at 300 Hz
  Bandwidth**                                  

  **Pulse Rate**     2 pps                     1 to 5 pps

  **Frequency        10 to 100 kHz             3 kHz to 3 MHz
  Range**                                      

  **Frequency        5%                        ≥ 100 Hz
  Steps**                                      

  **Coherent Integ.  8 seconds                 \> 2 seconds
  Time**                                       
  ------------------ ------------------------- ---------------------------

**Table 3.5** RPI Instrument Performance Parameters

RPI will have two crossed 500-m tip-to-tip thin wire dipole antennas in
the spin plane, and a 20-m tip-to-tip tubular dipole antenna along the
spin axis. All three antennas will be used for reception to determine
the angles of arrival of the echoes \[*Calvert et al.,* 1995\].

The large distances, low power, and short antennas (relative to the
wavelength) require onboard signal processing. Pulse compression and
coherent spectral integration techniques will be used to achieve the
required signal-to-noise (S/N) ratios. For a large part of the frequency
range, S/N is larger than 100, assuring 1o angular resolution. The range
resolution of 500 km is defined by the 3.2-ms width of the transmitted
sub-pulses. The number of sounding frequencies selected for a given
measurement, together with the coherent integration time, determines the
time resolution, since measurements are taken continuously.

**4.0 IMAGE End-to-End Data Flow**

The IMAGE mission will maintain a series of World Wide Web (WWW) pages
which provide the latest information about all aspects of IMAGE,
including the type and accessibility of IMAGE data. These pages are
located at the following URL: http://image.gsfc.nasa.gov/

4.1 Overview

Data will be nominally downlinked once per orbit using the DSN 34 meter
subnet and forwarded to the Science and Mission Operations Center (SMOC)
located at GSFC. Because of the volume of the data, and latency within
the DSN system, this transfer could take as long as nine hours but as
short as one hour. Once the data from an orbit have been delivered to
the SMOC, Level-0 and Level-1 science data processing will be initiated.
The resulting products will be made immediately available to anyone on
an IMAGE web site maintained in the SMOC. These products will also be
forwarded to the NSSDC for permanent archiving and public distribution.
See Figure 4.1 for a graphical description of the IMAGE data system.

4.2 Science and Missions Operations Center

The IMAGE observatory will be operated from the SMOC which is located at
GSFC. The Spacecraft Control Team will operate the SMOC and will perform
all mission operations including execution of the consolidated science
data plan provided weekly by the PI, spacecraft commanding and command
management, health and safety monitoring and control, Level-0 and
Level-1 science data processing, and data distribution. The
consolidation of all of these functions, which have been traditionally
been performed in separate facilities at GSFC, into a single facility
will minimize the size of the ground operations staff and the cost of
operations. Data services at the SMOC will include a WWW interface for
accessing the previous week's worth of IMAGE data and information
including Level-0 files for download, Level-1 files for download and/or
display, and data accounting and processing status information.

4.3 Data Products and Access Overview

This section will discuss all the IMAGE data products, how and where
they are generated, and how and when they will be accessible.

![](media/image2.pct){width="6.027777777777778in"
height="5.486111111111111in"}

4.3.1 Level-0 Data

Each Level-0 data file will consist of a time-ordered set of source data
packets from each instrument and a standard file header consistant with
the ISTP Level-0 Guidelines (560-1DFD/0190). Two Level-0 data files will
be generated for each instrument per orbit, a file of instrument science
data packets, and a file of instrument housekeeping packets. The SMOC
will post the most recent Level-0 data on the IMAGE web pages, in
addition to providing it on a daily basis to the NSSDC. A quicklook
version of each of these files will be generated immediately upon
receipt of data from DSN, and a final version will be generated 3 days
later, after recovering lost data.

4.3.2 Level-1 Data

In order to accomplish the IMAGE scientific goals, the ability to
quickly survey a vast array of scientific data being generated by each
instrument is essential. The result of Level-1 data processing in the
SMOC will typically be an image referred to as a Browse Product (BP).
All BP data sets are created as Common Data Format (CDF) files using the
ISTP Guidelines (see *Kessel et al*., 1994) for Key Parameter Data. The
SMOC will post the most recent BP data on the IMAGE web pages in
addition to providing it on a daily basis to the NSSDC. A quicklook
version of each of these files will be generated immediately upon DSN
pass completion. A delay of 3 days will occur if lost data needs to be
recovered from DSN. The Browse Product summaries for each IMAGE
instrument are given in Table 4.1.

The software algorithms for the BP production will be provided by each
of the instrument teams and will be integrated into the SMOC data
production pipeline prior to the launch. The software and associated
documentation for the BPs will be archived at the NSSDC.

4.3.3 Level-2 and Higher Level Data Products

Higher level IMAGE data products are being designed to illustrate
magnetospheric structures and dynamics. All binary higher level data
products will also be in the ISTP/Common Data Format. Each of the
instrument teams (IT) have facilities at their institution that are used
in processing, analyzing, and correlating IMAGE data. It is expected
that some IMAGE investigators will routinely generate additional
instrument data products. These products, along with associated
documentation and the generation software, will be delivered to the
NSSDC for long-term archiving and community-wide distribution. Table 4.2
provides a overview of the higher Level data products that have
currently been identified to be archived.

4.3.4 Attitude and Orbit Products

A daily attitude history file shall be produced in the SMOC. This file
will generated as an ISTP-standard CDF file, and will contain the
attitude quaternions as determined by the spacecraft on-board computer.
Orbit determination will be performed by the JPL/DSN and will be
retrieved via FTP by the SMOC, where it will be converted into an orbit
ISTP-standard CDF file containing spacecraft position and velocity
vectors. This data will also be delivered to the NSSDC for long-term
archiving and distribution.

4.4 Data Archiving and Distribution

The Level-0, Level-1, attitude and orbit data products will be sent via
FTP to the NSSDC daily for permanent archive and public distribution.
These data products will only be held temporarily in the SMOC until they
can be copied onto CD-ROM or DVD (Digital Versatile Disk) and sent to
selected IMAGE investigators and participating scientists. The
CD-ROMs/DVDs produced in the SMOC will conform to the ISO 9660 standard,
which defines both the physical and logical format of the CD-ROM/DVD.
This approach ensures that most CD-ROM/DVD drives on most platforms will
be able to read these disks. In addition, the CD-ROM/DVD produced by the
SMOC will follow other emerging NASA standards, guidelines, and
practices, especially the use of Standard Formated Data Unit (SFDU), and
a file naming and directory structure which will be compatible with most
platforms.

4.5 Archival Data Volume

The estimated volume of mission data acquired over nominal 2-year
lifetime (based on average bits per orbit, a 13.5 hour orbit, and
Level-1 &2 data products, which are estimated at 20% of the Level-0
volume) are shown in Table 4.3. The attitude and orbit data volume will
be approximately 2 GB total. Based on these estimates the total IMAGE
Observatory data volume to be archived at the NSSDC will be
approximately 280 GB over the 2-year lifetime of the mission.

4.6 Archive Data Access

The NSSDC's on-line archive facility that will be used for rapid access
to all the archived IMAGE data is called the NASA/NSSDC Data Archive and
Distribution Service, or NDADS. The purpose of the NDADS system is to
manage public archival data. Since the SMOC\'s primary purpose is to
process and distribute the most recent IMAGE data, the SMOC is not
designed to manage all the retrospective requests for older processed
and archived IMAGE data. Investigators using IMAGE data who desire
retrospective IMAGE data will be able to access the NSSDC's NDADS
archive. NDADS provides archival data services not only to IMAGE
scientists, but also to the worldwide science user community and the
public.

One of the most important features of the NDADS system is that it
provides the capability for scientists to retrieve data from the archive
by several methods. The public data archive can easily be accessed
through the NSSDC\'s automated retrieval mail system, or ARMS or the
WWW. The NDADS system is operational 24 hours/day, 7 days/week and is a
major archive and data distribution facility on the Space Physics Data
System.

**Table 4.1**; Level 1 Data Products (Browse Products)

**Table 4.2**; Higher Level Data Products

+------------------+--------------+-----------------+-----------------+
| > Instrument     | Level-0 (GB) | Level-1 (GB)    | Level-2 (GB)    |
+------------------+--------------+-----------------+-----------------+
| > LENA           | 4.0          | 0.8             | 0.8             |
+------------------+--------------+-----------------+-----------------+
| > MENA           | 23.7         | 4.7             | 4.7             |
+------------------+--------------+-----------------+-----------------+
| > HENA           | 21.9         | 4.4             | 4.4             |
+------------------+--------------+-----------------+-----------------+
| > RPI            | 67.5         | 13.5            | 13.5            |
+------------------+--------------+-----------------+-----------------+
| > EUV            | 19.1         | 3.8             | 3.8             |
+------------------+--------------+-----------------+-----------------+
| > FUV            | 51.7         | 10.4            | 10.4            |
+------------------+--------------+-----------------+-----------------+
| > CIDP           | 2.1          | 0.4             | 0.4             |
+------------------+--------------+-----------------+-----------------+
| > Spacecraft     | 7.8          | 1.6             | 1.6             |
+------------------+--------------+-----------------+-----------------+
| > **Total**      | **197.8 GB** | **40.0 GB**     | **40.0 GB**     |
+------------------+--------------+-----------------+-----------------+

**Table 4.3**; Estimated Volume of Mission Data and Data Products

**5.0 Data Rights and Rules for Data Use**

The IMAGE data are open to all scientists and the public. There are no
proprietary periods associated with any of the IMAGE data products. All
IMAGE data (including Level-0) will be archived at the NSSDC.

**6.0 References**

Anger, C. D., S. K. Babey, A. Lyle Broadfoot, R. G. Grown, L. L. Cogger,
R. Gattinger, J. W. Haslett, R. A. King, D. J. McEwen, J. S. Murphree,
E. H. Richardson, B. R. Sandel, K. Smith, and A. V. Jones, An
ultraviolet auroral imager for the Viking spacecraft, *Geophys. Res.
Letts.*, **14**, 387, 1987.

Calvert, W., R. F. Benson, D. L. Carpenter, S. F. Fung, D. Gallagher, J.
L. Green, P. H. Reiff, B. W. Reinisch, M. Smith, and W. W. L. Taylor,
The feasibility of radio sounding of the magnetosphere, *Radio Sci.*,
**30**, 5, 1577-1595, 1995.

Ghielmetti, A. G., E. G. Shelley, S. A. Fuselier, F. Herrero, M. F.
Smith, P. Wurz, P. Bochsler, and T. Stephen, A mass spectrograph for
imaging low energy neutral atoms, *Optical Engineering,* **33**, 362,
1993.

Kessel, R. L., R. E. McGuire, H. K. Hills, and N. J. Love, "CDF
Implementation Guidelines for ISTP", Version 2.3, February 7, 1994.

Wurz, P., M. R. Aellig, P. Bochsler, A. G. Ghielmetti, E. G. Shelley, S.
Fuselier, F. Herrero, M. F. Smith, T. Stephen, Neutral Atom Imaging Mass
Spectrograph, *Optical Engineering*, **34**, 2365, 1995.

**Acknowledgments**

Comments by William Taylor, Shing Fung, Mona Kessel, and Joseph King are
gratefully acknowledged. In addition, I would like to gratefully
acknowledge J. Burch and R. Burley for their extensive input into the
instrument and data system sections respectively.

**Appendix A- Acronym List**

ADAC - Attitude determination and control system

CDF - Common Data Format

CoI - Co-Investigator

COTS - Commercial Off-The-Shelf

DPS - Digisonde Portable Sounder

DSN - Deep Space Network

DVD - Digital Versatile Disk

EUV - Extreme Ultraviolet Imager

ESA - European Space Agency

fp - Plasma Frequency

FDF - Flight Dynamics Facility

FOV - Field of View

FTP - File Transfer Protocol

FUV - Far-Ultraviolet Imager

GB - Gigabytes

GCI - Geocentric Celestial Inertial Coordinate System

GSE - Geocentric Solar Ecliptic Coordinate System

GSM - Geocentric Solar Magnetospheric Coordinate System

GSFC - Goddard Space Flight Center

HENA - High-Energy Neutral Atom Imager

IMAGE - Imager for Magnetopause-to-Aurora Global Exploration

IT - Instrument Teams

LBH - Lyman-Birge-Hopfield (bands of FUV emissions from N2

LENA - Low-Energy Neutral Atom Imager

MENA - Medium-Energy Neutral Atom Imager

MCP - Multi-Channel Plate

MIDEX - Medium Explorer

MO&DA - Mission Operations and Data Analysis

NAI - Neutral Atom Imager

NASA - National Aeronautics and Space Administration

NASCOM - NASA Communication Network

NSI - NASA Science Internet

NSSDC - National Space Science Data Center

O I - Neutral atomic oxygen emission produced by electron impact

OSP - Orbiting Satellites Project

PI - Principal Investigator

PDMP - Project Data Management Plan

QL - Quicklook - Telemetry that is used to monitor health and safety of
S/C and instruments.

RE - Earth Radii

RPI - Radio Plasma Imager

S/N - Signal-to-noise

SEC - Space Evironment Center

SFDU - Standard Formatted Data Units

SMOC - Science and Mission Operations Center

SSR - Solid State Recorder

SwRI - Southwest Research Institute

TOF - Time of Flight

URL - Uniform Resource Locator

WIC - Far Ultraviolet Wideband Imaging Camera

WWW - World Wide Web