Imager for Magnetopause-to-Aurora
Global Exploration (IMAGE) 

Level 1 Requirements definition

FEBRUARY 18,1997

EXPLORER PROGRAM

OFFICE OF SPACE SCIENCE

NASA HEADQUARTERS

Imager for Magnetopause-to-Aurora
Global Exploration (IMAGE) 

Level 1 Requirements Definition

Approved by: ___________________________		Date:_________________
		Dr. G. Withbroe
		Science Program Director
		Sun-Earth Connection

Approved by: ___________________________		Date:_________________
		Dr. R. L. Carovillano
		Image Program Scientist

Approved by: ___________________________		Date:_________________
		W. T. Huddleston
		Image Program Executive

Table of Acronyms

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

1.	PURPOSE
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).
2.	PROGRAM REQUIREMENTS
In implementing the IMAGE program, the following principles apply:

á	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.
á	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. 
á	Mission will meet the Flight Assurance requirements for the Explorers Project.  
3.	MISSION OVERVIEW
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 Sciences, 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 NASA’s 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 NASA’s 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:

a)	Development of science requirements and the science mission plan;
b)	Development of the instrumentation and support systems;
c)	Procurement of the IMAGE spacecraft;
d)	Integration of the spacecraft and science payload;
e)	Support for the integration of the spacecraft to the Delta 7326 launch vehicle; 
f)	Initial on-orbit activation of the spacecraft including instruments;
g)	Training of the GSFC Flight Operations Team;
h)	Development and operation of the IMAGE science operations functions;
i)	Acquisition and validation of the data base and implementation of an open data policy for the mission;
j)	Development and execution of a comprehensive education and public outreach program featuring magnetospheric science;
k)	Analysis and publication of peer-review science publications; 
l)	Presentation of science results to the scientific community and the public at large; and
m)	Mission systems engineering and verification.

GSFC will be responsible for the following elements of the IMAGE program:

a)	Oversite of the MIDEX IMAGE mission on behalf of NASA;
b)	Procurement of the Delta 7326 launch vehicle; and 
c)	Development and operation of the Science and Mission Operations Center (SMOC).
4.	LEVEL 1 SCIENCE REQUIREMENTS
4.1	Scientific Objectives
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:

á	What is the mechanism for injecting plasma into the magnetosphere on substorm and magnetic storm time scales?
á	What is the directly driven response of the magnetosphere to solar wind changes?
á	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:
á	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;
á	Develop instrument specifications from the performance parameters;
á	Employ a strong systems engineering program to insure instrument performance specifications are designed into the instruments and the performance verified prior to integration;
á	Develop a spacecraft that supports the instrumentation and provides a reliable two-year mission;
á	Develop a Science and Mission Operations Center to acquire, process, and distribute IMAGE data in accord with the open data policy for the mission;
á	Operate the IMAGE spacecraft for two years on-orbit; and 
á	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.	LEVEL 1 DEVELOPMENT REQUIREMENTS
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: 90º  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 for each sensor.	
EUV	30.4 nm imaging of plasmasphere He+ column densities.		FOV: 90º  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 l = 140-190 nm (Wideband Imaging Camera, WIC) and l = 121.6 and 135.6 nm (Spectrographic Imager, SI)		FOV: 16º_ for aurora (image full Earth from apogee), 60 deg for geocorona. 
Spatial Resolution: 70 km (wideband camera),90 km (spectrographic imager
Spectral Resolution: separate cold geocorona H from hot proton precipitation (Dl~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]	0.01-0.3	1-30	10-500	
Energy resolution [_E/E]	0.8 E	0.8 E	 3kev	
Instantaneous FOV [deg]	890	4x107	90x120	
Total FOV [deg]	90360	107x360	120x360	
Pixel resolution [deg]	88	48	44	
Total G-factor [cm2sr]	0.2	0.07	1.6	
Pixel sensitivity
[cts/atom cm2sr eV/eV]	
710-4	
410-3	
4.510-3	
Image time [s] 	120	120	120	
Pixel array dimensions*	2M4E11A	2M16E 32A	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 Earth’s 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)	Aper-ture (mm2)	l (nm)	l Res. (nm)	Instant. FOV 
(deg)	Tot.
FOV (deg)	Pixel FOV (deg)	Sensi-tivity (c/R/
pixel)	Time Res. (min)	Spatial Res.
@7RE (km/pix)	
EUV	Plasmaspheric He+ 30.4 nm	75 	25 
( 3)	30.4	5.0	3090	90
360	0.5 0.5	2.4	2	640640	
FUV/SI	Auroral LBH (narrow band), Ly-a	68	112	121.8,
135.6	0.2,
3	1515	15 360	0.11	0.05	2	9090	
FUV/WIC
____
GEO	Auroral LBH (broad band)
_____________
Geocoronal 
Ly-a 

	22.4

_______
 60 

	60.8

______
 132	140–190
_____
121.6	N/A

_____
  0.2	30x22.5

______
1x1 (3
 cells)
	22.5x
360
______
60x360	0.09.

______
   1	0.1

_____
  0.1	2

_____
 2	70x70

_______
 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 msec	3.2 to 125 ms	
Receiver Bandwidth	300 Hz	fixed	
Pulse Rate	2 pps	1 to 5 pps	
Frequency Range	10 to 100 kHz 	3 kHz to 3 MHz	
Frequency Steps	5%	≥ 100 Hz	
Coherent Integ. Time	8 sec.	> 2 sec	
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 NASA’s 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.
6.	LEVEL 1 MISSION OPERATIONS REQUIREMENTS
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.	LEVEL 1 RESOURCE POLICY AND REQUIREMENTS
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:

á	Principal Investigator
á	Mission Manager
á	Mission Scientist

Principal Investigator recommended changes in co-investigators requires evaluation by the mission project office and OSS approval.