417-R-SEISSPORD-0030

**Geostationary Operational Environmental Satellite**

**(GOES)**

**GOES-R Series**

Space Environment In-Situ Suite (SEISS)

Performance and Operational Requirements Document (PORD)

Baseline Version 1.0

7/12/04

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[1. Scope 1](#scope)

[1.1. Identification 1](#identification)

[1.2. Mission Review 1](#mission-review)

[1.3. Document Overview 1](#document-overview)

[1.4. Terminology 2](#terminology)

[1.5 Definitions 2](#definitions)

[1.6 Requirement Applicability 3](#requirement-applicability)

[2. Applicable Documents 3](#applicable-documents)

[3. Sensor Requirements 3](#sensor-requirements)

[3.1. Sensor Definition 3](#sensor-definition)

[3.1.1. SEISS Modes 3](#seiss-modes)

[3.1.2.1 Safe Mode 4](#safe-mode)

[3.1.2.2 Normal Operational Mode 4](#normal-operational-mode)

[3.1.2.3 Instrument Diagnostic Mode 4](#instrument-diagnostic-mode)

[3.1.2. On-Orbit Operations 4](#on-orbit-operations)

[3.1.2.1. Reserved 5](#reserved)

[3.1.2.2. Reserved 5](#reserved-1)

[3.1.2.3. Eclipse 5](#eclipse)

[3.1.2.4. Operations After Maneuvers 5](#operations-after-maneuvers)

[3.1.2.4.1. Yaw Flip 5](#yaw-flip)

[3.1.2.4.2. Stationkeeping 5](#stationkeeping)

[3.1.2.5. Activation 5](#activation)

[3.1.2.6. On-Orbit Storage 5](#on-orbit-storage)

[3.2. Sensor Requirements 5](#sensor-requirements-1)

[3.2.1. General Requirements 5](#general-requirements)

[3.2.1.1. Noise 5](#noise)

[3.2.1.2. Stability 5](#stability)

[3.2.1.3. In-Flight Calibration 6](#in-flight-calibration)

[3.2.1.4. Ground Calibration 6](#ground-calibration)

[3.2.1.5. Out-of-Band Response 6](#out-of-band-response)

[3.2.2. MPS Requirements 6](#mps-requirements)

[3.2.2.1. Low Energy Electrons and Protons
6](#low-energy-electrons-and-protons)

[3.2.2.1.1. Flux Measurement Range 6](#flux-measurement-range)

[3.2.2.1.2. Accuracy 6](#accuracy)

[3.2.2.1.3. Spatial Coverage and Field of View
6](#spatial-coverage-and-field-of-view)

[3.2.2.1.4. Data Rate 6](#data-rate)

[3.2.2.1.5. Maximum and Minimum Flux 7](#maximum-and-minimum-flux)

[3.2.2.2. Medium and high energy electrons and protons
7](#medium-and-high-energy-electrons-and-protons)

[3.2.2.2.1. Measurement Range 7](#measurement-range)

[3.2.2.2.2. Accuracy 7](#accuracy-1)

[3.2.2.2.3. Spatial Coverage and Field of View
7](#spatial-coverage-and-field-of-view-1)

[3.2.2.2.4. Data Rate 8](#data-rate-1)

[3.2.2.2.5. Maximum and Minimum Flux 8](#maximum-and-minimum-flux-1)

[3.2.3. SGPS Requirements 8](#sgps-requirements)

[3.2.3.1. Measurement Range 8](#measurement-range-1)

[3.2.3.2. Accuracy 9](#accuracy-2)

[3.2.3.3. Spatial Coverage and Field of View
9](#spatial-coverage-and-field-of-view-2)

[3.2.3.4. Data Rate 9](#data-rate-2)

[3.2.3.5. Minimum and Maximum Flux 9](#minimum-and-maximum-flux)

[3.2.4. EHIS Requirements 9](#ehis-requirements)

[3.2.4.1. Measurement Range 9](#measurement-range-2)

[3.2.4.2. Accuracy 10](#accuracy-3)

[3.2.4.3. Spatial Coverage and Field of View
10](#spatial-coverage-and-field-of-view-3)

[3.2.4.4. Data Rate 10](#data-rate-3)

[3.2.4.5. Minimum and Maximum Flux 10](#minimum-and-maximum-flux-1)

[3.3. Design Requirements 10](#design-requirements)

[3.3.1. Reliability 10](#reliability)

[3.3.2. Mechanical Requirements 11](#mechanical-requirements)

[3.3.2.1. Design Limit Loads 11](#design-limit-loads)

[3.3.2.2. Non-Linear Loads 11](#non-linear-loads)

[3.3.2.3. Yield Strength 11](#yield-strength)

[3.3.2.4. Ultimate Strength 11](#ultimate-strength)

[3.3.2.5. Structural Stiffness 11](#structural-stiffness)

[3.3.2.6. Unit Stiffness 12](#unit-stiffness)

[3.3.2.7. Material Properties 12](#material-properties)

[3.3.2.8. Critical Members Design Values
12](#critical-members-design-values)

[3.3.2.9. Redundant Members Design Values
12](#redundant-members-design-values)

[3.3.2.10. Selective Design Values 12](#selective-design-values)

[3.3.2.11. Structural Reliability 12](#structural-reliability)

[3.3.2.12. Mechanisms 13](#mechanisms)

[3.3.2.13. Pressurized Units 13](#pressurized-units)

[3.3.2.14. Alignment Reference 14](#alignment-reference)

[3.3.3. Thermal Requirements 14](#thermal-requirements)

[3.3.3.1. Temperature Limits 14](#temperature-limits)

[3.3.3.2. Non Operational Temperature 14](#non-operational-temperature)

[3.3.3.3. Thermal Control Hardware 14](#thermal-control-hardware)

[3.3.4. On-Board Processor Requirements
14](#on-board-processor-requirements)

[3.3.4.1. Flight Load Non-volatile Memory
14](#flight-load-non-volatile-memory)

[3.3.4.2. Commandable Reinitialization
14](#commandable-reinitialization)

[3.3.4.3. Deterministic Power-on Configuration
14](#deterministic-power-on-configuration)

[3.3.4.4. Fail-safe Recovery Mode 14](#fail-safe-recovery-mode)

[3.3.5. Flight Software Requirements 15](#flight-software-requirements)

[3.3.5.1. Language and Methodology 15](#language-and-methodology)

[3.3.5.2. Software Module Upload 15](#software-module-upload)

[3.3.5.3. Flexibility and Ease of Software Modification
15](#flexibility-and-ease-of-software-modification)

[3.3.5.4. Version Identifiers 15](#version-identifiers)

[3.3.5.5. Flight Processor Resource Sizing
15](#flight-processor-resource-sizing)

[3.3.5.6. Software Event Logging 16](#software-event-logging)

[3.3.5.7. Warm Restart 16](#warm-restart)

[3.3.5.8. Memory Tests 16](#memory-tests)

[3.3.5.9. Memory Dump 16](#memory-dump)

[3.3.5.10. Telemetry 16](#telemetry)

[3.3.6. Power Requirements 17](#power-requirements)

[3.3.6.1. Power Regulators and Supplies
17](#power-regulators-and-supplies)

[3.3.6.2. Fuses 17](#fuses)

[3.3.6.3. Test Connectors 17](#test-connectors)

[3.3.7. Magnetic Properties 17](#magnetic-properties)

[3.3.8. Spacecraft Level Ground Testing
17](#spacecraft-level-ground-testing)

[3.3.9. Ground Support Equipment and Development Facilities
17](#ground-support-equipment-and-development-facilities)

[3.3.9.1. Electrical System Test Equipment
17](#electrical-system-test-equipment)

[3.3.9.2. Flight Software Development Environment
18](#flight-software-development-environment)

[3.3.9.3. Shipping Container 18](#shipping-container)

[4. Acronyms 18](#acronyms)

#  {#section .unnumbered}

# Scope

## Identification

This Performance and Operational Requirements Document (PORD) sets forth
the performance requirements for the National Oceanic and Atmospheric
Administration (NOAA) Space Environment In-Situ Suite (SEISS).

## Mission Review

The SEISS particle sensors **shall** monitor the proton, electron, and
heavy ion fluxes at geosynchronous orbit. These particle fluxes roughly
consist of three components: 1) a geomagnetically trapped and highly
variable population of electrons and protons; 2) sporadic fluxes of
electrons, protons, and heavy ions of direct solar origin (e.g. from
flares); and 3) a background of galactic cosmic rays ranging from
several MeV to highly relativistic energies. Knowledge of the near-Earth
energetic particle environment is important in establishing the natural
radiation hazard to humans at high altitudes and in space, as well as
risk assessment and warning of episodes of surface charging, deep
dielectric charging, and single event upset of satellite systems.
Energetic particle precipitation into Earth's ionosphere also causes
disturbance and disruption of radio communications and navigation
systems.

The SEISS particle sensors **shall** include a magnetospheric particle
sensor (MPS), a solar and galactic proton sensor (SGPS), and an
energetic heavy ion sensor (EHIS).

The SEISS objectives are as follows:

-   Provide data essential to NOAA's Space Weather Operations and to the
    long-term record of changing conditions in the space environment.

-   Maintain continuity with measurements provided in past and current
    Geostationary Operational Environmental Satellite (GOES) Series
    Spacecraft.

-   Provide multiple measurements characterizing the charged particle
    population, including measurements of the electron, proton, and
    heavy ion fluxes.

-   Be in Normal Operational Mode during on orbit storage, through
    eclipse, and spacecraft maneuvering.

## Document Overview

This document contains all performance requirements for the SEISS suite
of instruments and Ground Support Equipment (GSE). This document, the
General Interface Requirements Document (GIRD), and the SEISS Unique
Instrument Interface Document (UIID) define all instrument to spacecraft
interfaces for the SEISS.

## Terminology

The term "(TBD)", which means "to be determined", applied to a missing
requirement means that the instrument contractor determines the missing
requirement.

The term "(TBR)", which means "to be refined/reviewed", means that the
requirement is subject to review for appropriateness and subject to
revision. The contractor is liable for compliance with the requirement
as if the "TBR" notation did not exist. The "TBR" merely provides an
indication that the value is more likely to change in a future
modification than requirements not accompanied by a "TBR".

## Definitions

Throughout this document, the following definitions apply:

[Accuracy:]{.underline} Refers to the error in a measurement, that is
the difference between the measured and true value. It includes both
systematic and random errors. Systematic errors must be estimated from
an analysis of the experimental conditions and techniques. Random errors
can be determined, and reduced, through repeated measurements under
identical conditions and a standard deviation calculated. The magnitude
of a random error shall be taken as three standard deviations (3σ).

[All requirements/all performance requirements/ all operational
requirements]{.underline}: Refers to any performance characteristic or
requirement in the GIRD, SEISS PORD, SEISS UIID.

[Cadence]{.underline}: The time interval between the start of successive
data collection sequences.

[Data Latency]{.underline}: The time interval between the end of a data
collection sequence and the time that the data is available at the
spacecraft interface.

[Eclipse]{.underline}: Defined as when the solar disk is occulted by the
Earth or Moon, as viewed from the spacecraft.

[Flux]{.underline}: The number of particles crossing a unit area from a
unit solid angle in a unit time. The directional-differential flux is
given in units: (cm^2^ s sr keV)^-1^ or (cm^2^ s sr MeV)^-1^ and the
directional-integral flux is given in units: (cm^2^ s sr)^-1^.

[Goal]{.underline}: A requirement that is desirable to achieve.

[Launch]{.underline}: The period of time between lift off and the
separation of the GOES-R series satellite from the launch vehicle.

[Station keeping]{.underline}: On-orbit spacecraft maneuver that
corrects for orbital drifts.

[Threshold:]{.underline} A requirement that must be met.

[Transfer Orbit]{.underline}: The sequence of events that transpires to
establish the GOES-R series satellite on-station after the GOES-R series
satellite has separated from the launch vehicle.

[Unit]{.underline}: A functional subdivision of a subsystem and
generally a self-contained combination of items performing a function
necessary for the subsystem's operation. Examples are electronics unit
and sensor unit.

[Yaw Flip]{.underline}: An on-orbit maneuver that rotates the spacecraft
180º about the spacecraft z axis (yaw). The net effect reverses the
signs of the roll and pitch axes while maintaining yaw pointing at
nadir.

## Requirement Applicability

All requirements apply over the entire life of the SEISS.

Data performance requirements in this SEISS PORD apply to data after all
ground processing, except as indicated.

# Applicable Documents

Various parts of this requirements document refer to some of these
documents.

[Structural Design and Test Factors of Safety for Spaceflight
Hardware]{.underline}, NASA, Document Number NASA-STD-5001, June 21,
1996.

[General Specification for Assemblies, Moving Mechanical, for Space and
Launch Vehicles]{.underline}, Document Number MIL-A83577B, February 1,
1988.

Space Mechanisms Handbook, Document Number NASA TP-1999-206988.

[General Environmental Verification Specification for STS and ELV
Payloads, Subsystems and Components]{.underline}, Document Number GSFC
GEVS-SE, June 1, 1996.

[Eastern and Western Range Policies and Procedures]{.underline},
Document Number EWR-127-1, October 23, 2000.

[Standard General Requirements for Safe Design and Operation of
Pressurized Missile and Space Systems]{.underline}, Document Number
MIL-STD-1522, September 4, 1992.

# Sensor Requirements

## Sensor Definition

### SEISS Modes

The SEISS **shall** execute commands to individually enable and disable
each autonomous function of the SEISS.

All SEISS instruments **shall** individually and independently accept
commands.

The SEISS instruments **shall** provide operation mode telemetry at the
same rate as the instrument science data.

The SEISS instruments **shall** initiate all commanded mode transitions
in no more than 20 seconds after receipt of command.

The SEISS instruments **shall** provide limits and triggers of
autonomous functions that are changeable by command.

The SEISS instruments **shall** transition from the current mode to any
other mode without causing permanent damage to themselves.

The SEISS instruments **shall** provide command and housekeeping
telemetry functions in all powered modes.

#### Safe Mode

Each SEISS instrument **shall** provide a Safe Mode.

The SEISS instruments **shall** provide a thermally and optically safe
configuration for an indefinite period of time while in Safe Mode.

The SEISS instruments **shall** provide an autonomous command function
to enter Safe Mode upon detection of instrument contractor defined
internal faults capable of causing permanent damage to the instrument.

The SEISS instruments **shall** enter safe mode upon command.

The SEISS Instruments **shall** transition to Safe Mode, whether
commanded or autonomous, in no more than 1 second.

The SEISS shall transition from Safe Mode to Normal Operational Mode in
no more than 10 minutes.

#### Normal Operational Mode

All SEISS instruments **shall** provide a Normal Operational Mode.

#### Instrument Diagnostic Mode

Each SEISS instrument **shall** provide an Instrument Diagnostic Mode.

The SEISS shall perform the following functions while operating in the
Instrument Diagnostic Mode.

-   Download RAM contents.

-   TBD

-   Send dwell data (increased samples per second of a particular
    telemetry measurand).

### On-Orbit Operations

The SEISS shall operate normally, within specification, while flying
aboard a 3-axis stabilized, geostationary spacecraft with orbital limit
constraints as stated in the GIRD and UIID.

#### Reserved

#### Reserved

#### Eclipse

The SEISS **shall** continuously operate without reduction in
performance during eclipse periods.

#### Operations After Maneuvers

##### Yaw Flip

The SEISS **shall** continuously operate without reduction in
performance during and after a yaw flip.

##### Stationkeeping

The SEISS **shall** continuously operate without reduction in
performance while the spacecraft performs stationkeeping maneuvers.

#### Activation

The SGPS and EHIS **shall** be turned on within TBD minutes following
launch.

The MPS **shall** be turned on within TBD minutes following launch.

The SEISS instruments **shall** meet all requirements within 30 minutes
of SEISS turn on.

#### On-Orbit Storage

The SEISS **shall** continuously operate without reduction in
performance during on orbit storage.

## Sensor Requirements

### General Requirements

The requirements in this section apply to all instruments of the SEISS.

#### Noise

For bands below 30 keV, the total instrument noise **shall** not exceed
10% of a band's threshold energy.

For bands with threshold energies between 30 keV and 100 keV, the total
instrument noise **shall** not widen the effective response by more than
10 keV.

For bands above 100 keV, total instrument noise **shall** not widen the
effective response by more than 10% of a band's threshold energy.

#### Stability

The SEISS **shall** provide individual electronic discriminator levels
defining the energy band upper and lower edges that do not change by
more than ±3% over the predicted operating conditions.

#### In-Flight Calibration

The SEISS instruments **shall** provide an in-flight calibration mode
that verifies basic instrument operation and determines the value of the
energy band edges.

The SEISS **shall** determine electronic discriminator levels with an
accuracy of ±3%.

The SEISS in-flight calibration **shall** be both self-terminating and
able to be terminated by ground command.

#### Ground Calibration

The instruments **shall** be fully characterized prior to delivery,
including the measurement of the instrument response to in-band
(including direction, energy, and species) and out-of-band particles.

The energy dependent and the directional responses of the instruments
**shall** be determined for energies ranging from below the detector's
low-energy threshold to energies for which the particle flux is below
the instrument detection threshold.

#### Out-of-Band Response

The SEISS **shall** limit the response to out-of-band particles
(including direction, energy, and species), in any channel to no more
than 10% of the response to in-band particles.

### MPS Requirements

#### Low Energy Electrons and Protons

##### Flux Measurement Range

The MPS **shall** provide low energy electron and proton flux
measurements in the range 30 eV to 30 keV.

The MPS **shall** determine the proton and electron flux in 15 evenly
spaced logarithmic energy bands per species.

##### Accuracy

The MPS **shall** provide a flux measurement accuracy of 25% (Goal 10%),
determined through ground calibration.

##### Spatial Coverage and Field of View

The MPS **shall** provide at least five non-overlapping and equally
spaced bins in the YZ plane.

The field of view **shall** be 170 degrees in the YZ plane, 30 degrees
(TBR) in the XZ plane, and symmetric about the XZ and YZ planes.

The coordinate system is referenced to the spacecraft BRF axes defined
in GIRD paragraph 3.1.4-2.

##### Data Rate

The MPS refresh rate **shall** be at least once per 30 seconds.

The MPS data latency **shall** be less than 5 seconds. (TBR)

##### Maximum and Minimum Flux

The MPS shall detect the minimum flux with a minimum of 10 counts above
background in each energy channel for measurements taken over a 5 minute
interval.

The MPS output **shall** not decrease as the flux increases up to three
times the specified maximum flux.

> **a) Electrons**
>
> The MPS **shall** measure the electron flux according to the following
> energy spectra (*E* is the energy in keV):
>
> Minimum flux:
>
> 0.03 -- 30keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 9. x 10^4^
> *E*^-1.3^
>
> Maximum flux:
>
> 0.03 -- 30keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 1.5 x 10^9^
> *E*^-1.3^
>
> **b) Protons**
>
> Minimum flux:
>
> 0.03 -- 30keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 40. *E*^-0.8^
>
> Maximum flux:
>
> 0.03 -- 30keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 1.1 x 10^7^
> *E*^-0.8^

#### Medium and high energy electrons and protons

##### Measurement Range

The MPS **shall** measure electron flux in the range of 30 keV to 4 MeV.

The MPS **shall** determine the electron flux in 10 evenly spaced
logarithmic energy bands plus one integral channel for energies greater
than 2 MeV.

The MPS **shall** measure proton flux in the range of 30 keV to 1 MeV.

The MPS **shall** determine the proton flux in 7 evenly spaced
logarithmic energy bands.

##### Accuracy

The MPS **shall** provide a flux measurement accuracy of 25% (Goal 10%),
determined through ground calibration.

##### Spatial Coverage and Field of View

The MPS **shall** provide at least five non-overlapping and equally
spaced bins in the YZ plane.

The field of view **shall** be 170 degrees in the YZ plane, 30 degrees
(TBR) in the XZ plane, and symmetric about the XZ and YZ planes.

The coordinate system is referenced to the spacecraft BRF axes defined
in GIRD paragraph 3.1.4-2.

##### Data Rate

The refresh rate **shall** be at least once per 30 seconds.

The data latency **shall** be less than 5 seconds. (TBR)

##### Maximum and Minimum Flux

The MPS **shall** detect the minimum flux with a minimum of 10 counts
above background in each energy channel for measurements taken over a 5
minute interval.

The MPS output **shall** not decrease as the flux increases up to three
times the specified maximum flux.

> **a) Electrons**
>
> The MPS **shall** measure the electron flux according to the following
> energy spectra (*E* is the energy in keV):
>
> Minimum flux:
>
> 30-- 4,000 keV: Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 1.2 x 10^7^
> *E*^-2.8^
>
> Maximum flux:
>
> 30-- 4,000 keV: Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 2.3 x 10^11^
> *E*^-2.8^
>
> **b) Protons**
>
> The MPS **shall** measure the proton flux according to the following
> energy spectra (*E* is the energy in keV):
>
> Minimum flux:
>
> 30-- 1,000 keV: Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 8. x 10^2^
> *E*^-1.8^
>
> Maximum flux:
>
> 30-- 1,000 keV: Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 5 x 10^7^
> *E*^-1.3^

### SGPS Requirements

#### Measurement Range

The SGPS **shall** provide proton flux measurements in the energy range
from 1 MeV to 500 MeV.

As a threshold, the flux **shall** be determined in 10 evenly spaced
logarithmic energy bands up to 500 MeV.

As a goal, the SGPS **shall** provide proton flux measurements \>500
MeV.

As a goal, one integral channel **shall** be provided for flux
measurements \> 500 MeV.

#### Accuracy

The SGPS **shall** provide a flux measurement accuracy of 25% (Goal
10%), determined through ground calibration.

#### Spatial Coverage and Field of View

The SGPS shall consist of two identical sensor heads, each with a field
of

view of 60 degrees in XY plane, 60 degrees in the XZ plane, and
symmetric

about the XY and XZ planes, with the +X or the -X axis as the view

direction.

The coordinate system is referenced to the spacecraft BRF axes defined
in GIRD paragraph 3.1.4-2.

#### Data Rate

The refresh rate **shall** be at least once per 1 minute.

The data latency **shall** be less than 5 seconds. (TBR)

#### Minimum and Maximum Flux

The SGPS **shall** resolve the largest likely solar particle event. The
spectrum for this event can be represented as (E is the energy in keV):

> Minimum flux:
>
> 1,000 -- 500,000 keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 8. x 10^2^
> *E*^-1.8^
>
> Maximum flux:
>
> 1,000 -- 500,000 keV Flux \[cm^-2^ s^-1^ sr^-1^ keV^-1^\] = 2. x
> 10^12^ *E*^-2.8^

The SGPS **shall** detect the minimum flux with a minimum of 10 counts
above background in each energy channel for measurements taken over a 5
minute interval.

The SGPS output **shall** not decrease as the flux increases up to three
times the specified maximum flux.

### EHIS Requirements

#### Measurement Range

The EHIS **shall** provide flux measurements in the energy range from 10
MeV/nucleon to 200 MeV/nucleon.

The EHIS **shall** detect and distinguish between the following mass
groups: He, C-N-O, Ne-S, and the Fe group.

The flux within each mass group **shall** be determined in 5 evenly
spaced logarithmic energy bands within the specified range.

#### Accuracy

The EHIS **shall** provide a flux measurement accuracy of 25% (Goal
10%), determined through ground calibration.

#### Spatial Coverage and Field of View

The EHIS **shall** have a conical field of view with a half angle of 30
degrees (TBR) about the minus Z axis of the spacecraft BRF specified in
GIRD paragraph 3.1.4-2.

#### Data Rate

The refresh rate **shall** be at least once per 5 minutes.

The data latency **shall** be less than 5 seconds. (TBR)

#### Minimum and Maximum Flux

The EHIS **shall** measure the heavy ion abundances during the largest
likely solar particle event. The minimum and maximum fluxes within each
of the four mass bands can be represented as (E is the energy in MeV):

> Maximum Flux: Flux \[cm^-2^ s^-1^ sr^-1^ (MeV/nuc)^-1^\] = 5 x 10^4^
> (*E/nuc)* ^-2.3^
>
> Threshold:
>
> Minimum Flux: Flux \[cm^-2^ s^-1^ sr^-1^ (MeV/nuc)^-1^\] = 1.1 x
> 10^-2^ (*E/nuc)* ^-1^
>
> Goal:
>
> Minimum Flux: Flux \[cm^-2^ s^-1^ sr^-1^ (MeV/nuc)^-1^\] = 2.7 x
> 10^-3^ (*E/nuc)* ^-1^

The EHIS **shall** detect the minimum flux with a minimum of 10 counts
above background in each energy channel for measurements taken over a 5
minute interval.

The EHIS output **shall** not decrease as the flux increases up to three
times the maximum flux.

##  Design Requirements

### Reliability

The SEISS **shall** have a Reliability (R) of at least 0.6 after 10
years of on-orbit operations, preceded by up to 5 years of ground
storage and up to 5 years of operation during on-orbit storage.

The SEISS **shall** have a Mean Mission Duration (MMD) of 8.4 years for
a design life of 10 years.

The SEISS units of any Flight Model **shall** be interchangeable,
without modification, with the equivalent units of any other SEISS
Flight Model.

The SEISS **shall** withstand without damage the sudden removal of
operational power.

### Mechanical Requirements

Each SEISS unit structure **shall** possess sufficient strength,
rigidity and other characteristics required to survive the critical
loading conditions that exist within the envelope of handling and
mission requirements.

#### Design Limit Loads

The structure **shall** be capable of withstanding all limit loads
without loss of any required function.

Limit loads are defined as all worst case load conditions including
temperature effects from the environments expected during all phases of
the structure's service life including manufacturing, ground handling,
transportation, environmental testing, integration, pre-launch, launch
and on-orbit operations and storage.

#### Non-Linear Loads

The SEISS structures **shall** be capable of withstanding redistribution
of internal and external loads resulting from any non-linear effects
including deflections under load.

#### Yield Strength

The SEISS structures **shall** be able to support yield loads without
detrimental permanent deformation. Yield loads are limit loads
multiplied by the appropriate protoflight yield factor of safety
specified in [NASA-STD-5001]{.underline}. For structural elements
containing beryllium or beryllium alloys, the prototype yield factor of
safety is 1.4.

While subjected to any operational load up to yield operational loads,
the resulting deformation **shall** not interfere with the operation of
the SEISS flight units. Operational load is defined as the expected
on-orbit loads while the SEISS is operating.

#### Ultimate Strength

The SEISS structures **shall** be able to support ultimate loads without
fracture or collapse for at least 3 seconds including ultimate
deflections and ultimate deformations of the flight unit structures and
their boundaries. However, when proof of strength is shown by dynamic
tests simulating actual load conditions, the 3-second limit does not
apply. Ultimate loads are limit loads multiplied by the appropriate
protoflight ultimate factor of safety specified in
[NASA-STD-5001]{.underline}. For structural elements containing
beryllium or beryllium alloys, the prototype ultimate factor of safety
is 1.6.

#### Structural Stiffness

Stiffness of the SEISS unit structures and their attachments **shall**
be designed by consideration of their performance requirements and their
handling, transportation and launch environments.

Special stowage provisions **shall** be used if required to prevent
excessive dynamic amplification during handling, transportation and
transient flight events.

#### Unit Stiffness

The fundamental resonant frequency of each SEISS flight unit **shall**
be 50 Hz or greater when the flight unit is constrained at its
spacecraft interface.

#### Material Properties

Material properties **shall** be based on sufficient tests of the
material meeting approved specifications to establish design values on a
statistical basis.

Design values **shall** account for the probability of structural
failures and loss of any required function due to material variability.

The instrument contractor **shall** specify the source and statistical
basis of all material properties used in the design.

#### Critical Members Design Values

For critical members, design values **shall** be selected to assure
strength with a minimum of 99 percent probability and 95 percent
confidence.

Structural members are classified as critical when their failure would
result in loss of structural integrity of the flight units.

#### Redundant Members Design Values

For redundant members, design values **shall** be selected to assure
strength with a minimum of 90 percent probability and 95 percent
confidence.

Structural members are classified as redundant when their failure would
result in the redistribution of applied loads to other structural
members without loss of structural integrity.

#### Selective Design Values

As an exception to Sections "Critical Members Design Values" and
"Redundant Members Design Values", greater design values may be used if
a representative portion of the material used in the structural member
is tested before use to determine that the actual strength properties of
that particular structural member will equal or exceed those used in the
design.

#### Structural Reliability

The strength, detailed design, and fabrication of the structure
**shall** prevent any critical failure due to fatigue, corrosion,
manufacturing defects and fracture throughout the life of the SEISS
resulting in the loss of any mission objective.

Accounting for the presence of stress concentrations and the growth of
undetectable flaws, the SEISS structures **shall** withstand loads
equivalent to four complete service lifetimes.

While subjected to any flight operational load up to limit flight
operational loads, the resulting deformation of the residual SEISS
structures **shall** not interfere with the operation of the SEISS.

After any load up to limit loads, the resulting permanent deformation of
the residual instrument flight unit structures **shall** not interfere
with the operation of the SEISS.

#### Mechanisms

Deployment, sensor, pointing, drive, separation mechanisms and other
moving mechanical assemblies may be designed using
[MIL-A-83577B]{.underline} and [NASA TP-1999-206988]{.underline}.

All SEISS mechanisms **shall** meet performance requirements while
operating in an earth gravity environment with any orientation of the
gravity vector.

Moving mechanical assemblies **shall** have torque and force ratios per
section 2.4.5.3 of [GEVS-SE]{.underline} using a NASA approved
classification of each instrument mechanism.

For all operating points of the actuators, all rotational actuators
**shall** have available a continuous maximum torque output greater than
7.0 milli-Newton meters.

For all operating points of the actuators, all linear actuators
**shall** have available a continuous maximum force output greater than
0.28 N.

For SEISS mechanisms using closed-loop control, gain and phase margins
**shall** be greater than 12 dB, and greater than 40 degrees,
respectively. The margins **shall** include the effects of the dynamic
properties of any flexible structure.

All SEISS mechanisms requiring restraint during launch **shall** be
caged during launch without requiring power to maintain the caged
condition.

All SEISS mechanisms requiring restraint **shall** be released from a
caged condition by command.

All SEISS mechanisms requiring restraint **shall** be returned to a
caged condition ready for launch by either command or by manual
actuation of an accessible caging device.

#### Pressurized Units

SEISS pressurized systems **shall** follow the requirements in
accordance with [EWR-127-1]{.underline} and [MIL-STD-1522A]{.underline}
for the design of pressurized systems.

The SEISS **shall** have no open fluid reservoirs when delivered to the
spacecraft contractor.

####  Alignment Reference

The SEISS sensor units **shall** have fiduciary marks locating the X, Y,
and Z axes of the units.

### Thermal Requirements

#### Temperature Limits

The SEISS contractor **shall** establish Mission Allowable Temperatures
(MAT) for the SEISS with at least 5 K of analytical/test uncertainty.

Thermal margin is defined as the temperature delta between MAT versus
the bounding predictions plus analytical uncertainty*.*

The SEISS **shall** maintain thermally independent units and their
internal components within MAT limits during all flight operational
conditions including bounding worst-case environments.

#### Non Operational Temperature 

The Non-Operational Temperatures (NOT) range **shall** extend at least
20 K warmer than the hot MAT and at least 20 K colder than the cold MAT.

The cold Non-Operational Temperature **shall** be 248K or colder.

#### Thermal Control Hardware

There **shall** be two or more serial and independent controls for
disabling any heater where any failed on condition would cause
over-temperature conditions or exceed the instrument power budget.

The SEISS heaters **shall** be sized to have 25% margin for worst case
conditions.

The SEISS survival heaters **shall** be thermostatically controlled.

### On-Board Processor Requirements

####  Flight Load Non-volatile Memory

The entire flight software image **shall** be contained in non-volatile
memory at launch.

####  Commandable Reinitialization 

The On-Board Processor shall provide for reset by command.

#### Deterministic Power-on Configuration 

The On-Board Processor **shall** initialize upon power-up into a
predetermined configuration.

#### Fail-safe Recovery Mode

The Instrument **shall** provide a failsafe recovery mode dependant on a
minimal hardware configuration capable of accepting and processing a
minimal command subset sufficient to load and dump memory.

### Flight Software Requirements

#### Language and Methodology 

All software developed for the SEISS **shall** be developed with
ANSI/ISO standard languages and a widely-accepted, industry-standard,
formal software design methodology. Minimal use of processor-specific
assembly language is permitted for certain low-level programs such as
interrupt service routines and device drivers with NASA approval.

#### Software Module Upload

The flight software **shall** be reprogrammable on-orbit without
computer restart.

The flight software **shall** be capable of being uploaded in Computer
Software Units (CSUs) and is usable immediately after completion of the
modified unit upload.

Activation of the modified CSUs **shall** not require completion of an
upload of the entire flight software image.

#### Flexibility and Ease of Software Modification 

The SEISS flight software **shall** be deterministic in terms of
scheduling and prioritization of critical processing tasks to ensure
their timely completion.

All software data that are modifiable and examinable by ground operators
**shall** be organized into tables that can be referenced by table
number so table data can be loaded and dumped by the ground without
reference to memory address.

The definition of instrument commands within the ground database
**shall** not be dependent on physical memory addresses within the
flight software.

#### Version Identifiers 

All software and firmware versions **shall** be implemented with an
internal identifier (embedded in the executive program) that can be
included in the instrument engineering data.

This software identifier **shall** be keyed to the configuration
management process.

#### Flight Processor Resource Sizing

During development, flight processors providing computing resources for
instrument subsystems **shall** be sized for worst case utilization not
to exceed the capacity shown below (measured as a percentage of total
available resource capacity):

> Flight Processor Resource Utilization Limits

  ---------------------- ---------------- --------------- ----------------
                         S/W PDR          S/W CDR         S/W AR

  RAM Memory             40%              50%             60%

  ROM Memory             50%              60%             70%

  CPU                    40%              50%             60%
  ---------------------- ---------------- --------------- ----------------

#### Software Event Logging

The flight software **shall** include time-tagged event logging in
telemetry.

The event messages **shall** include all anomalous events, mode
transitions, and system performance events.

All flight software components **shall** utilize a common format for
event messages.

The flight software **shall** provide a means for ground command to
enable and disable queuing of individual event messages.

The flight software **shall** buffer a minimum of 1000 event messages
while the event messages are queued for telemetering to the ground.

The event message queue **shall** be configurable by command to either
(a) discard the new events, or (b) overwrite oldest events when the
queue is full.

The flight software **shall** maintain counters for:

a)  the total number of event messages generated

b)  the number of event messages discarded because of queue overflow

c)  the number of event messages not queued due to being disabled.

#### Warm Restart

The flight software **shall** provide a restart by command with
preservation of the event message queue and memory tables.

#### Memory Tests

The flight software **shall** provide a mechanism to verify the contents
of all memory areas.

#### Memory Dump 

The flight software, and associated on-board computer hardware,
**shall** provide the capability to dump any location and any size of
on-board memory to the ground upon command.

The flight software memory dump capability **shall** not disturb normal
operations and instrument data processing.

#### Telemetry

Telemetry points sampled by the instrument **shall** be controlled by an
on-orbit modifiable table.

The sample rate of every instrument telemetry point **shall** be
controlled by an on-orbit modifiable table.

### Power Requirements

#### Power Regulators and Supplies

The SEISS power regulators and supplies **shall** have a phase margin of
greater than 35 degrees.

The SEISS power regulators supplies across the spacecraft **shall** have
a gain margin of greater than 20 dB.

#### Fuses

The SEISS **shall** not contain fuses.

#### Test Connectors

The SEISS **shall** have flight qualified covers for all test point
connectors.

### Magnetic Properties

The change in the magnetic field produced by the SEISS sensor,
electronics, or power supply modules **shall** be less than 30 nanoTesla
peak-to-peak for any operating mode, up to a single low pass bandwidth
of 1.0 Hz, in any axis when measured at a distance of 1 meter from any
face of a module.

### Spacecraft Level Ground Testing

The SEISS **shall** accommodate operational testing in all modes and
states for indefinite periods during Spacecraft level Thermal Vacuum in
at least the following two orientations:

1.  Spacecraft +Y axis aligned with the gravity vector and pointed down.

2.  Spacecraft --X axis aligned with the gravity vector and pointed
    down.

### Ground Support Equipment and Development Facilities

#### Electrical System Test Equipment

The Electrical System Test Equipment (ESTE) **shall** operate the SEISS
and ground support equipment during performance verification and
calibration testing.

The ESTE **shall** simulate the spacecraft interface with power, clock
pulses, command, and telemetry functions.

The ESTE **shall** include all test equipment necessary to operate and
control the SEISS in all phases of operation and test modes.

The ESTE **shall** generate and maintain command logs.

The ESTE **shall** limit check all health and safety data.

The ESTE **shall** capture and archive all raw SEISS data.

The ESTE **shall** provide near-real time and off line data analysis of
all SEISS data necessary to determine the performance characteristics of
the instrument.

The ESTE **shall** interface with the Spacecraft Ground Support
Equipment at the Spacecraft Contractor's facility to extract SEISS
science and engineering data.

The ESTE **shall** prohibit hazardous or critical commands being sent to
the SEISS without operator verification.

#### Flight Software Development Environment

The Flight Software Development Environment (FSDE) **shall** consist of
the hardware and software systems used for realtime, closed loop testing
on flight like hardware to develop, test, validate, and demonstrate the
flight software is ready for Government acceptance.

The FSDE **shall** support all lifecycle activities (development, test,
and validation) simultaneously.

The FSDE **shall** contain all items (software, databases, compilers,
debuggers, etc.) needed to prepare flight software for the target
processor.

The FSDE **shall** contain engineering (hardware) models of necessary
flight hardware as well as dynamic software models comprising the
remainder of the instrument and the necessary on-orbit environment.

#### Shipping Container

The SEISS shipping container **shall** be compatible with shipment by
air or air-ride van.

The SEISS shipping container **shall** be climate controlled and
purgable.

The SEISS shipping container **shall** have internal temperature,
humidity, and pressure monitors with external indicators.

The SEISS shipping container **shall** have shock recorders.

The SEISS shipping container **shall** meet all contamination control
requirements imposed on the SEISS instrument units.

The SEISS shipping container **shall** be painted white and stenciled to
indicate NASA property, content, and structural certification.

The SEISS GSE shipping containers shall be compatible with shipment by
air or air-ride van.

The SEISS GSE shipping containers shall be painted white and stenciled
to indicate NASA property, content, and structural certification.

# Acronyms

  ---------- --------------------------------------------------------------
  ACA        After Contract Award

  AI         Action Item

  AIR        Action Item Review

  ANSI/ISO   American National Standards Institute / International
             Organization of Standards

  AR         Acceptance Review

  BRF        Body Reference Frame

  CCP        Contamination Control Plan

  CDR        Critical Design Review

  CMP        Configuration Management Plan

  CMS        Configuration Management System

  CPU        Central Processing Unit

  CSU        Computer Software Unit

  dB         Decibel

  DOORS      Dynamic Object-Oriented Requirements System

  EHIS       Energetic Heavy Ion Sensor

  ESD        Electro-Static Discharge

  ESTE       Electrical System Test Equipment

  FMEA       Failure Mode Effects Analysis

  FMECA      Failure Mode Effects and Criticality Analysis

  FMP        Financial Management Plan

  FPCCR      Formulation Phase Concept and Cost Review

  FSDE       Flight Software Development Environment

  FTA        Fault Tree Analysis

  GIRD       General Interface Requirements Document

  GOES       Geostationary Operational Environmental Satellite

  GSE        Ground Support Equipment

  GSFC       Goddard Space Flight Center

  Hz         Hertz

  ICD        Interface Control Document

  IV&V       Independent Verification and Validation

  K          Kelvin

  MAID       Master Action Item Database

  MAR        Mission Assurance Requirements

  MAT        Mission Allowable Temperature

  MeV        Mega Electron Volts

  MLI        Multilayer Insulation

  MMD        Mean Mission Duration

  MPS        Magnetospheric Particle Sensor

  MRD        Mission Requirements Document

  MTR        Midterm Review

  N          Newton

  NASA       National Aeronautics and Space Administration

  NOAA       National Oceanic and Atmospheric Administration

  NOT        Non-Operational Temperature

  OBP        On-Board Processor

  PDR        Preliminary Design Review

  PMP        Project Management Plan

  PORD       Performance and Operational Requirements Document

  PR         Progress Review

  PRA        Probabilistic Risk Assessment

  R          Reliability

  RA         Recommended Approach

  RAM        Random Access Memory

  RFA        Request for Action

  RFI        Request for Information

  RMP        Risk Management Plan

  ROM        Read Only Memory

  S/W        Software

  SDP        Software Development Plan

  SEISS      Space Environment In-Situ Suite

  SEL        Single Event Latch-up

  SEMP       Systems Engineering Management Plan

  SEP        Systems Engineering Process

  SEU        Single Event Upset

  SGPS       Solar and Galactic Proton Sensor

  SLOC       Software Lines of Code

  SOW        Statement of Work

  TBD        To Be Determined

  TBR        To Be Reviewed

  TRL        Technology Readiness Level

  TS         Trade Study

  UIID       Unique Instrument Interface Document

  VP         Verification Plan
  ---------- --------------------------------------------------------------