IMAGER FOR MAGNETOPAUSE-TO-AURORA
GLOBAL EXPLORATION (IMAGE)
LEVEL 1 REQUIREMENTS DEFINITION
February 18, 1997
Explorer Program
Office of Space Science
NASA Headquarters
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Approved by:
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Dr. G. Withbroe, Science Program Director, Sun-Earth Connection
Dr. R. L. Carovillano, IMAGE Program Scientist
W. T. Huddleston, IMAGE Program Executive
Contents
- Purpose
- Program Requirements
- Mission Overview
- Level 1 Science Requirements
- Level 1 Development Requirements
- Level 1 Mission Operations Requirements
- Level 1 Resource Policy and Requirements
- Acronyms
This document contains the Level 1 requirements for the development of the
Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) investigation.
Concurrent with the initiation of the development phase, the Level 1 requirements
will be incorporated into the IMAGE Program Plan as approved by the Associate
Administrator for the Office of Space Science (OSS) and the Director of the
Goddard Space Flight Center (GSFC).
In implementing the IMAGE program, the following principles apply:
- The IMAGE mission will be developed using the Level 1 requirements as a
baseline. A Confirmation Review, to be conducted prior to the initiation
of the development phase, will confirm mission content and the Level 1
requirements.
- The total cost for IMAGE (all phases) will not exceed the agreed to cost
cap upon which the mission was selected, and the launch date will be no
later than March 2000. As described in Paragraph 7.1, IMAGE mission scope
is to be considered a parameter to control mission cost and schedule.
- Mission will meet the Flight Assurance requirements for the Explorers Project.
3.1 Contributions of IMAGE to Magnetospheric Science
In-situ measurements made for the past 35 years have yielded a wealth of statistical
information about the magnetosphere and its constituent plasma regimes. These
measurements have also provided many examples of dynamic changes of magnetospheric
plasma parameters at specific times and places in response to changes in the
solar-wind input and to internal disturbances related to substorms. However,
statistical global averages and individual events are not sufficient to understand
the dynamics and interconnections of this highly dynamic system. Fundamental
questions concerning plasma entry into the magnetosphere, global plasma circulation
and energization, and the global response of the magnetospheric system to internal
and external forcing functions remain unanswered. Furthering our understanding of
the physical processes that affect the magnetosphere requires the nearly instantaneous
measurement of its topology, that is, magnetospheric imaging.
The overall objective of the IMAGE mission is to determine the global response of
the magnetosphere to changing conditions of the solar wind. To address these basic
questions, IMAGE will provide imaging of three general magnetospheric regions:
a) the magnetopause, boundary layer, cusp, and auroral zone; b) the plasmasphere;
and c) the inner plasma sheet, ring current, and trapped radiation. IMAGE will
also provide images of near-Earth interplanetary space. The data acquired in each
of these regions will be used to determine the global structure of the magnetosphere,
characterize the connectivity between magnetospheric regions, and place results in a
global context with previous in-situ measurements.
Significant international participation is planned as follows:
| Institution |
Provision |
Institute of Space and Astronautical Science,
Tokyo, Japan |
Microchannel plate detector systems for the MENA instrument |
Rutherford Appleton Laboratories,
England |
High-voltage power supplies for MENA |
University of Bern,
Switzerland |
Design and test of conversion surface in LENA |
Liege Space Center,
Belgium |
Optical and mechanical design of the FUV SI |
University of Calgary,
Canada |
Design of the FUV WIC instrument housing and optics and calibration of WIC |
Observatoire de Paris,
Meudon, France |
Provide antenna couplers for RPI |
Max Planck Institute for Aeronomy,
Lindau, Germany |
Provide geocorona oxygen cells (GEO) for FUV |
3.2 IMAGE Mission Structure
The P.I., Dr James Burch, is accountable to NASA for the scientific success of
the investigation. In accordance with NASAšs transfer of program management
responsibility to its Centers, Explorer program management responsiblility has
been assigned to GSFC. In this role, GSFC is responsible for the exercise of
NASAšs fiduciary responsibility to ensure that Explorer missions are achieved
in compliance with committed cost, schedule, performance, reliability, and
safety requirements. The Principal Investigator and his support team at Southwest
Research Institute (SwRI), will be responsible for the overall management of the
investigation. With the assistance from the Co-Investigator institutions, SwRI
will be responsible for the following elements of the overall program:
- Development of science requirements and the science mission plan;
- Development of the instrumentation and support systems;
- Procurement of the IMAGE spacecraft;
- Integration of the spacecraft and science payload;
- Support for the integration of the spacecraft to the Delta 7326 launch vehicle;
- Initial on-orbit activation of the spacecraft including instruments;
- Training of the GSFC Flight Operations Team;
- Development and operation of the IMAGE science operations functions;
- Acquisition and validation of the data base and implementation of an open data policy for the mission;
- Development and execution of a comprehensive education and public outreach program featuring magnetospheric science;
- Analysis and publication of peer-review science publications;
- Presentation of science results to the scientific community and the public at large; and
- Mission systems engineering and verification.
GSFC will be responsible for the following elements of the IMAGE program:
- Oversite of the MIDEX IMAGE mission on behalf of NASA;
- Procurement of the Delta 7326 launch vehicle; and
- Development and operation of the Science and Mission Operations Center (SMOC).
The overall science objective of IMAGE is the determination of 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) at 121-190 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.
4.2 Approach for Accomplishing Science Objectives
The IMAGE approach to accomplishing the science objectives listed above include
the following key steps:
- Model magnetospheric processes in order to establish a set of performance
parameters for the various imaging techniques (NAI, FUV, EUV, RPI) and to
verify the required orbit;
- Develop instrument specifications from the performance parameters;
- Employ a strong systems engineering program to insure instrument performance
specifications are designed into the instruments and the performance verified
prior to integration;
- Develop a spacecraft that supports the instrumentation and provides a reliable
two-year mission;
- Develop a Science and Mission Operations Center to acquire, process, and
distribute IMAGE data in accord with the open data policy for the mission;
- Operate the IMAGE spacecraft for two years on-orbit; and
- Develop and execute an aggressive program of education and public outreach to
insure the widest possible understanding and use of IMAGE data.
4.3 Allocation of Mission Time
The IMAGE mission will operate with a near 100% duty cycle with all instruments in
their baseline operational modes. The minimum time resolution for all instruments
except the RPI will be set by the spacecraft spin period of two minutes. Longer-term
average images over multiple spin periods can be constructed on the spacecraft or
later on the ground. The IMAGE Science Team will have the responsibility to collect
and validate the data but claim no proprietary data rights, and the mission will
therefore operate in a facility mode.
4.4 Minimum Mission Success Criteria
To meet its minimum success criteria, IMAGE will require the MENA and HENA instruments,
the EUV instrument, and either the FUV Spectrographic Imager (SI) or the Wideband
Imaging Camera (WIC) to function properly and meet the science objectives as stated
in Table 1. With this complement of core instruments, IMAGE will be able to accomplish
essential science objectives identified for the mission. With the data provided by the
core instruments, IMAGE will be able to obtain images of the ring current as it builds
up and decays over the course of magnetic storms. It will also obtain images of the
plasmasphere, the outer portions of which are stripped away during magnetic storms and
subsequently replenished from the ionosphere. The FUV images will provide the dynamical
context by the determination and mapping of the global auroral activity that accompanies
the magnetic storms. Achievement of these objectives during a single magnetic storm will
constitute the minimum success criterion for IMAGE.
5.1 Flight Segment
5.1.1 Spacecraft
5.1.1.1 Mission and Instrument Support
Requirements for the IMAGE spacecraft have been specified in SwRI document 8089-SPEC-01,
Spacecraft Functional Performance Specification. The spacecraft must be spin stabilized
(~0.5 rpm) in order to provide the fields of view needed by the instruments to image the
magnetosphere. The spacecraft must provide power, telemetry and command resources needed
to support the IMAGE science payload operation in an orbit of approximately 1000 km perigee
by a 7 Earth radii apogee. The spacecraft is required to accommodate a science instrument
deck plate of approximately 2.2 m diameter. All seven IMAGE instruments (Far Ultraviolet
Spectrographic Imager, Far Ultraviolet Wideband Imaging Camera, Extreme Ultraviolet Imager,
High Energy Neutral Atom Imager, Medium Energy Neutral Atom Imager, Low Energy Neutral Atom
Imager, and Radio Plasma Imager) and a Central Instrument Data Processor (CIDP) will be
mounted to the deck plate. The deck plate must be mechanically secured to the spacecraft
bus structure. Thermal control of the integrated deck plate must be provided by the
spacecraft thermal control system. An integrated purge manifold secured to the deck plate
will maintain a steady purge on the instruments up to launch.
5.1.1.2 Performance Assurance
A headquarters mission classification will not be issued for the IMAGE mission.
Performance assurance requirements for the spacecraft are specified by NASA documents
GSFC-410-MIDEX-001, and GSFC-410-MIDEX-002. The spacecraft will withstand the radiation
dose accumulated during the 2-year mission with at least a 50% margin.
5.1.2 Science Instrumentation
The types of instrumentation needed for IMAGE to meet its science objectives (see
Paragraph 4.1 for a discussion of science objectives) are listed in
Table 1 below.
| Image |
Measurement |
Critical Measurement Requirements |
| NAI |
Neutral atom composition and energy-resolved images over three energy ranges:
10-300 eV (LENA)
1-30 keV (MENA)
10-200 keV (HENA) |
FOV: 90° 90 (image ring current at apogee).
Angular Resolution: 8 8.
Energy Resolution (E/E): 0.8 (trade resolution for sensitivity).
Composition: distinguish H and O in magnetospheric and ionospheric sources,
interstellar neutrals and solar wind.
Image Time: 5 minutes (resolve substorm development).
Sensitivity: effective area 1 cm2
|
| EUV |
30.4 nm imaging of plasmasphere He+ column densities. |
FOV: 90° 90 (image plasmasphere from apogee).
Spatial Resolution: 0.1 Earth radius from apogee.
Image Time: several minutes to hours (resolve plasmaspheric processes). |
| FUV |
Far ultraviolet imaging of the geocorona (Geocorona Oxygen Cell) and the aurora
at lambda = 140-190 nm (Wideband Imaging Camera, WIC) and lambda = 121.6 and
135.6 nm (Spectrographic Imager, SI) |
FOV: 16° for aurora (image full Earth from apogee), 60° for geocorona.
Spatial Resolution: 70 km (wideband camera),90 km (spectrographic imager)
Spectral Resolution: separate cold geocorona H from hot proton precipitation
(Delta-lambda~0.2 nm near 121.6 nm); reject 130.4 nm and select 135.6 nm
electron aurora emissions.
Image Time: 2 minutes (resolve auroral activity). |
| RPI |
Remote sensing of electron densities and magnetospheric boundary locations using
radio sounding. |
Density range: 0.1-105 cm-3 (determine electron density from
inner plasmasphere to magnetopause).
Spatial resolution: 500 km (resolve density structures at the magnetopause and
plasmapause).
Image Time: 1 minute (resolve changes in boundary locations).
|
Table 1. Instrumentation Required to Meet Science Objectives |
5.1.2.1 NAI Instrument Performance Requirements (LENA,MENA,HENA)
Science instrumentation for IMAGE consists of the 7 instruments and the CIDP mentioned
above in paragraph 5.1.1.1. The performance requirements for the
NAI instruments are shown in Table 2 below.
| |
LENA |
MENA |
HENA |
| Energy range [keV] |
0.1-0.3 |
1-30 |
10-500 |
| Energy resolution [Delta-E/E] |
0.8 E |
0.8 E |
3 keV |
| Instantaneous FOV [degrees] |
8 x 90 |
4 x 107 |
90 x 120 |
| Total FOV [degrees] |
90 x 360 |
107 x 360 |
120 x 360 |
| Pixel resolution [degrees] |
88 |
48 |
44 |
| Total G-factor [cm2-sr] |
0.2 |
0.07 |
1.6 |
Pixel sensitivity
[counts/atom-cm2-sr-eV/eV] |
7 x 10-4 |
4 x 10-3 |
4.5 x 10-3 |
| Image time [s] |
120 |
120 |
120 |
| Pixel array dimensions* |
2M4E11A |
2M16E32A |
4M16E32A |
| 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 2. NAI Instrument Performance Parameters |
5.1.2.2 Photon Imagers (EUV,FUV)
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 Earthšs electron
and proton auroral emissions. The Geocorona Oxygen Cell (GOC) images the hydrogen
geocorona. General characteristics of the imagers are listed in
Table 3 below.
| Inst. |
Measurement Type |
Focal Length (mm) |
Aperture (mm2) |
Wavelength (nm) |
Wavelength Resolution (nm) |
Instant FOV (deg) |
Total FOV (deg) |
Pixel FOV (deg) |
Sensitivity (c/R/pixel) |
Time Res. (min) |
Spatial Res. at 7RE (km/pix) |
| EUV |
Plasmaspheric He+ 30.4 nm |
75 |
25 (3) |
30.4 |
5.0 |
30 x 90 |
90 x 360 |
0.5 x 0.5 |
2.4 |
2 |
640 x 640 |
| FUV/SI |
Auroral LBH (narrow band), Lyman-alpha |
68 |
112 |
121.8, 135.6 |
0.2, 3 |
15 x 15 |
15 x 360 |
0.11 |
0.05 |
2 |
90 x 90 |
| FUV/WIC |
Auroral LBH (broad band) |
22.4 |
60.8 |
140 - 190 |
N/A |
30 x 22.5 |
22.5 x 360 |
0.09 |
0.1 |
2 |
70 x 70 |
| GEO |
Geocoronal Lyman-alpha |
60 |
132 |
121.6 |
0.2 |
1 x 1 (3 cells) |
60 x 360 |
1 |
0.1 |
2 |
N/A |
Table 3. Photon Imager Instrument Performance Parameters |
5.1.2.3 Radio Plasma Imager (RPI)
The performance parameters for the radio plasma imager to meet science objectives are
listed in Table 4 and Table 5 below.
| 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 sec./frequency |
4 sec./frequency |
Table 4. RPI Measurement Performance Parameters |
| Parameter |
Nominal |
Limits |
| RF Power |
10 W |
10 W |
| Pulse Width |
53 ms |
3.2 - 125 ms |
| Receiver Bandwidth |
300 Hz |
fixed |
| Pulse Rate |
2 pps |
1 - 5 pps |
| Frequency Range |
10 - 100 kHz |
3 kHz - 3 MHz |
| Frequency Steps |
5% |
>= 100 Hz |
| Coherent Integration Time |
8 s |
>2 s |
Table 5. RPI Instrument Performance Parameters |
5.2 Launch Segment
The launch vehicle for IMAGE will be a Delta 7326, three-stage, expendable launch vehicle.
The launch site will be NASAšs Western Test Range (WTR) at Vandenberg AFB, California.
The launch date for IMAGE will be no later than March 2000. IMAGE will be launched into
an orbit of approximately 1000 km perigee by 7 Earth radii apogee.
5.3 Ground Segment
The Science and Mission Operations Center for IMAGE will be located at the GSFC with
support from the National Space Science Data Center (NSSDC). The mission will require
the use of the 34-meter deep space network.
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 radial wire antennas. At a time to be determined, the spacecraft
will deploy the two axial antennas. The full deployment of the antennas should take
<50 days.
After antenna deployment IMAGE will remain in an inertially fixed orbit for the full
two years of the planned mission. No maneuvers will be required to maintain solar aspect
for the duration of the mission. Commanding of IMAGE instruments will be required once
per week after initial activation and checkout. Ground contact after initial activation
will be once per orbit for a period of approximately 30 minutes each.
7.1 Cost Containment Agreement
The IMAGE P.I. has agreed to cap the cost of the IMAGE investigation excluding launch
vehicle at 68.0M in FY94 dollars for all activities through launch plus 30 days.
Mission Operations and Data Analysis activities (MODA) are capped at $15M in FY94 dollars.
7.2 Scope Reduction
If necessary to keep IMAGE costs within the cost cap, the P.I. has developed to a two-tier
descoping process. The first tier of descoping will take place if an individual instrument
or subsystem experiences a cost or schedule problem. This descoping option is specified in
Table 6 below. Further descoping will require Tier 2 descope options
shown in
Table 7 below. Any scope reductions will be implemented only after
consultation with the
Mission Manager and the Mission Scientist. Any potential scope reductions affecting
Level 1 Requirements will require approval by OSS NASA headquarters prior to their
execution.
| Descope |
Science Impact |
Latest Date |
| Elimination of Z and/or Y axis antennas |
Loss of three (3) dimensional imaging capability |
CDR |
| Elimination of mass analysis from LENA or MENA |
Loss of composition information in neutral atom images |
CDR for maximum savings |
| Restriction of MENA energy range |
Reduction of overlap of energy ranges of MENA and HENA |
Anytime, but CDR for maximum savings |
| Elimination of solid-state detectors from HENA |
Reduction of mass resolution |
CDR |
Table 6. Tier 1 Descoping Options |
| Descope |
Science Impact |
Latest Date |
| Elimination of RPI |
Loss of magnetopause topology
Loss of plasmasphere total ion contours
Loss of continuous monitor of cusp location |
Anytime, but in order to save most cost the decision to execute this
option should be made prior to CDR |
| Elimination of LENA |
Loss of NAI images of cusp ion fountain |
Same as above |
| Elimination of either SI or WIC |
Loss of SI would result in loss of high spectral resolution.
Loss of WIC would result in inability to image aurora well during
very quiet times. |
Same as above |
Table 7. Tier 2 Descoping Options |
7.3 Key Position
The following individuals are key to the success of IMAGE and will not be changed without
agreement from GSFC and the OSS:
- Principal Investigator
- Mission Manager
- Mission Scientist
Principal Investigator recommended changes in co-investigators requires evaluation by the
mission project office and OSS approval.
ADAC Attitude Determination and Control System
C&DH Command and Data Handling
CDR Critical Design Review
CCSDS Consultative Committee for Space Data Systems
CIDP Central Instrument Data Processor
COTS Commercial Off-The-Shelf
DPS Digisonde Portable Sounder
DSN Deep Space Network
EEE Electrical, Electronic, Electromechanical
EMC Electromagnetic Compatibility
EMI Electromagnetic Interference
EOL End of Life
EUV Extreme Ultraviolet Imager
FOV Field of View
FSS Fan Sun Sensor
FUV Far Ultraviolet Imager
GSFC Goddard Space Flight Center
HENA High-Energy Neutral Atom Imager
IMAGE Imager for Magnetopause-to-Aurora Global Exploration
LBH Lyman-Birge-Hopfield (bands of FUV emissions from N2
LENA Low-Energy Neutral Atom Imager
LEO Low Earth Orbit
MCP Microchannel Plate
Med-Lite Medium-Light Expendable Launch Vehicle
MENA Medium-Energy Neutral Atom Imager
MET Mission Elapsed Time
MI Magnetosphere Imager
MIDEX Medium Explorer
NAI Neutral Atom Imager
NASA National Aeronautics and Space Administration
PA Performance Assurance
QA Quality Assurance
QAE Quality Assurance Engineer
RAAN Right Ascension of the Ascending Node
RE Earth Radius
RPI Radio Plasma Imager
S/C Spacecraft
SI Far Ultraviolet Spectrographic Imager
SMOC GSFC Science and Mission Operations Center
S/N Signal-to-Noise
SSD Solid State Detector
SwRI Southwest Research Institute
VME Versamodule Europe
WIC Far Ultraviolet Wideband Imaging Camera