The Shuttle Black Scatter Ultraviolet Experiment Pamphlet

8/14/2019 The Shuttle Black Scatter Ultraviolet Experiment Pamphlet

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The ShuttleSolar BackscatterUltraviolet Experiment

BARTH SCIENCE AND APPLICATIONS DIVISION

NAS

1.2:Sh

9/16

0830-C


2/6

An Issue of Global Ozone Change...

Oz on e deplet ion in the uppe r at mos phe re is an issue

of increasing concern:

In 1985, the British Antarc tic Survey an n ou nc ed the

discovery of an ozo ne 'hol e 'o ver Antarct ica dur in g theaustral spr ingt i me. As of 1987, seas onal dep let i on w a s

as high as 60 percent in some areas over Antarctica.

In Ma rc h 1988, the NASA -led Oz on e Trends Pan el

repor ted that sinc e 1970, total oz on e has d ecr eas ed

by 1.7 to 3 percent over the latitudes covering the

Uni ted S tates , J a pa n, the Sov ie t Un ion, and Europ e .

Given ozone's role in shielding the Earth from

harmful ultraviolet radiation and controlling

stratospheric temperature, these findings have

worldwide health and environmental implications.

Concern over the thinning of the ozone layer has

sparked increased emphasis on developing and

improving ozone measurement methods and

instruments. Accur ate, reliable mea sur eme nts from

space, critical to the detecti on of predict ed oz on e

trends, also will form a basis for assessment of

potential effects and development of corrective

measures.

Measuring Ozone

Via the SBUV Instrument...

Oz on e monitoring efforts of NA SA an d NO A A rely

on space-based Solar Backscatter Ultraviolet ( SBU V)

instruments, which measure the total amount and

height distribution of ozone in the upper atmos

phere. The original S BU V instrument fl ew on N ASA 's

Nimbus-4 satellite, demonstrating the effectiveness

of the technique. The SBUV instrument aboard

NASA's Nimbus-7 satellite provided an 8-year data

set that will be continued into the late 1990s by the

SBUV/2 aboard NOAA's TIROS satell ites.

Percentage change in global ozone by month and latitude between

1980 and 1987, as measured by the Total Ozone Mapping Spectrome

ter (TOMS) and corrected to ground observations of total ozone. The

red area at bottom represents the Antarctic ozone "hole."

Ozone is derived from the SBUV/2 instrument from the ratio of ob

served backscattered radiance (IX) to the solar irradiance (FX) in the

ultraviolet. This ratio is termed the ultraviolet albedo.

The SBUV instrument measures solar irradiance and

radiation backscattered from the Earth's atmosphere

in 12 discrete wa ve le ng th cha nnel s in the ultraviolet.

Since ozone absorbs radiation in the ultraviolet

wav ele ngt hs, its am ou nt can be derived from the

rstlo of backscattered radiation to incident solar

radiation. Variations in backscattered radiation

indicate the vertical distribution of ozone in the

atmosphere.

The SBUV technique has proven to be a reliable

method of measuring ozone and solar ultraviolet

irradiance. However, problems do exist with

calibration drift an d instrument degr ada tio n ov er

time. The extremely precise measurements required

to accurately measure and ma p global ozo ne an d

solar irradiance make the calibration question a

critical one.


3/6

r in late 1989, with

3hout th e 1990s.

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hs co incident w ith

r ation until 1996

Der Shuttle mission

3tion to compare w ith

ic ident measurements

ments, equivalent to

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Dgram represents a

y to enhance th e

3-term environmen-

space-based

gular observations

)ard th e Shuttle also

readings of globa l

ination o ftrends a n d

oved models of ozone

derstanding o f o zo n e

e lo pm e n t of

venting or mit igat ing

dation

/ program, contact:

Investigator,

ibelt, Maryland 2 0 7 7 1 ,

isphere Research

;hington, D.C. 2 0 5 4 6

The ShuttleSolar BackscatterUltraviolet Experimen

An Issue ofGlobal Ozone Change...

Ozone depletion in the upper atmosphere is a n issue

of increasing concern:

In 1985, th e British Antarctic Survey annou nce d th e

discovery of an ozon e 'hole' over Antarctica duri ng t h e

austral springtime. As of 1987, seasonal depletion w a s

as high as 60 percent in some areas over Antarctica.

In M a rch 1988, the NASA- led Ozone Trends Pane l

reported that since 1970, total ozone h a s decreased

by 1.7 to 3 percent over th e latitudes covering th e

United Sta tes, Japan, th e Sov ie t Union, a n d Europe.

Given ozone's role in shielding th e Earth from

harmful ultraviolet radiation a n d controlling

stratospheric temperature, these findings have

wor ldwide hea l th a n d environmental implications.

Concern over th e thinning of the ozone layer ha s

sparked increased emphasis on developing a n d

improving ozone measurement methods a n d

instruments. Accurate, reliable measurements from

space, critical to the detection of predicted ozone

trends, also will form a basis fo r assessment of

potential effects a n d development of corrective

measures.

J F M A M J J A

MONTH

S O N D

Measuring Ozone

Via the SBUV Instrument...

Ozone monitoring efforts of NASA a n d NOAA rely

on space-based Solar Backscatter Ultraviolet (S BUV)

instruments, which measure th e total amount a n d

height distribution of ozone in the upper atmos

phere. The original SBUV instrument flew on NASA's

Nimbus-4 satellite, demonstrating th e effectiveness

of th e technique. Th e SBUV instrument aboard

NASA's Nimbus-7 satellite provided a n Q-ye^r data

set that will be continued into th e late 1990s by the

SBUV/2 aboard NOAA's TIROS satellites.

RTH SCIENCE AMD APPLICAT IONS DIVISION

Percentage change in global ozone by month and latitude between1980 and 1987, as measured by the Total Ozone Mappi ng Spectrome

ter (TOMS) and corrected to ground observations oftotal ozone. The

red area at bottom represents the Antarctic ozone "hole."

Ozone is derived from the SBUV/2 instrument from the ratio of ob

served backscattered radiance (l\) to the solar irradiance (FX) in th e

ultraviolet. This ratio is termed the ultraviolet albedo.

The SB UV inst rument measures solar irradiancea n d

radiation backscattered from th e Earth's atmosphere

in 12 discrete wav ele ngt h channels in th e ultraviolet.

Since ozone absorbs radiation in the ultraviolet

wavelengths, its amount can be derived from th e

rdtlo of backscattered radiation to incident solar

radiation. Variations in backscattered radiation

indicate th e vertical distribution of ozone in the

atmosphere.

The SBUV technique has proven to be a reliable

method of measuring ozone a n d solar ultraviolet

irradiance. However, problems d o exist with

calibration drift a n d instrument degradation over

time. The extremely precise measurements required

to accurately measure a n d m a p global ozone a n d

solar irradiance make th e calibration question a

critical o n e .


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Solution to SBUV Calibration Drift. The SSBUV Instrument.

To solve data reliability problems resulting from

calibration drift, NASA has developed and tested the

Shutt le Solar Backscatter Ultraviolet (SSBUV)

instrument. During regular Shuttle flights, SBUV/2

performance can be assessed by direct comparison

of data from both the SSBUV and SBUV/2 instruments

viewing nearly the same Earth locat ion. Whereas

previous calibration processes have relied solely on

ground-based reference standards and instruments,

this procedure will permit calibration in space

supplemented by a rigorous program of laboratory

calibration before and after each SSBUV flight.

Selected SSBU V and SBUV/2 orbit coincidences. A coincidence is de

fined when observations over a given point can be taken by both

instruments within 60 minutes. These coincidences will occur 16 times

daily over the dur ation of the experiment. Numbers indicate the inter

val (in minutes) between satellite observations.

At coincid ental orbit points, the SBUV /2 and S SB UV

instruments will make correlative measurements of

ozone parameters. SSBUV data will be used to assess

the degree of calibration drift in the SBUV/2

instrument. Based on these data, and on ground-

based measurements, corrections to the SBUV/2 data

wi l l be made.

SSBUV measurements wi l l also be compared with

measurements from other solar radiat ion-measuring

instruments aboard the Shuttle and the Upper

Atmosphere Research Satellite [UARSJ.

Like its SBUV /2 comp ani on, the SSB UV consists of

tw o 'A-meter Ebert-Fastie monochr omat ors

arranged consecu tively to reject stray light from the

spectral field of measurement. At the Goddard Space

Flight Center (GSFC) SSBUV facility, features were

added to the SBUV/2 prototype instrument to satisfy

Shuttle flight requirements:

A transmission diffuser w a s installed to transmit

sunl ight to the SSBU V sensor modu le

Solar and nadir aspect sensors w e re de v e lo pe d to

measure the SSBU V instrument's incl ina t ion towar d the

Sun and Earth dur ing observat ion per iods

An in-flight calibration system wa s de v e lo pe d a n d

installed to perfor m SS BU V instr ument calibrati on

check s an d accou nt for calibrat ion drift

Top view of the SSBUV instrument. The in-flight calibration system is

situated in the center, surrounded by solar and nadir aspect sensors.

The red plate covers the instrument entrance aperture.

MOTORIZED# DOOR MECHANISM

INSTRUMENT* CANISTER

JSSBUV flight configuration: two canisters house the instrument and

its support module. Each canister stands about 4 ft (1.2 m). The entire

configuration weighs about 1000 lbs (450 kg).

The SSBUV Payload. Maintaining S

The need for regular observations aboard the

Shuttle required the SSBUV instrument to be

designed as largely self-supporting, needing only

a few simple Shuttle interfaces. The result is a

virtual stand-alone experiment, mountable in

various locations within the Shuttle bay.

The SSBUV instrument and its dedicated

electronics, power, data, and com man d systems

are mounted into two canisters. The Instrument

Canister holds the instrument and its specially

designed aspect sensors and in-flight calibration

system. A Motorized Door Assembly (MD A)

opens to allow the SSBUV instrument to view the

Sun and Earth, and closes during the in-flight

calibration sequenc e. The MD A also prevents

contamination from the orbiter environment.

A flight microprocesso r reformats all SS BU V dat a

and provides instrument control during flight.

Instrument functions are initially commanded by

the Shuttle crew, then sequenced by the

microprocessor through about 30 operating

modes.

Th e Support Canister, l inked to the Instrument

Canister by a single cable, contains the power

system, data storage, and c omm an d decoders.

The dedicated power system can operate the

SSBUV payload for a total of about 40 hours.

The SSBUV experi

of laboratory and

calibration syste

developed by NA

response from th

the time it return

and mercury lam

and performs on-

calibration check

command of the

A special CalibraGSFC to develop

and maintain a s

capability (see flo

contains all the

perform accurate

instrument for the

refurbished Nim

will be use d as a l

by tracking the rc

calibration of the

intercomparisons

solar-ultraviolet r

to be flown on t

LABORATORY CONTROLLED ENVIRONMENT

AND SPA CE SIMULAT IONS

STANDARDS

SSBUV

LABORATORY

REFEREN CE

INSTRUMENT

PRE-FLIGHT

CALIBRATION

POST-FLIGHT

CALIBRATION

SPACE FLIGHT

SSBUV

IN-FLIGHTCALIBRATIONS


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Solution to SBUV Calibration Drift. Maintaining SSBUV Calibration.

To solve data reliability problems resulting from

calibration drift, NASA has developed and tested the

Shuttle Solar Backscatter Ultraviolet (SSBUV)

instrument. During regular Shuttle flights, SBUV/2

performance can be assessed by direct comparison

of data from both the SSBUV and SBUV/2 instruments

v i ew ing nearly the same Earth location. Whereas

previous calibration processes have relied solely on

ground-based reference standards and instruments,

this procedure will permit calibration in space

supplemented by a rigorous program of laboratory

calibration before and after each SSBUV flight.

Selected SSBUV and SBUV/2 orbit coincidences. A coincidence is defined when observations over a given point can be taken by both

instruments within 60 minutes. These coincidences will occur 16 times

daily over the duration of the experiment. Numbers indicate the inter

val (in minutes) between satellite observations.

At coinc ident al orbit points, the SBU V/2 an d SS BU V

instruments will make correlative measurements of

ozone parameters. SSBUV data will be used to assess

the degree of calibration drift in the SBUV/2

instrument. Based on these data, and on ground-

based measurements, corrections to the SBUV/2 data

wil l be made.

SSBUV measurements wi l l a lso be compared with

measurements from other solar radiation-measuring

instruments aboard the Shuttle and the Upper

Atmosphere Research Satellite (UARS).

The SSB U V expe riment consists of a uni qu e p rog ram

of laboratory and \ n -orb \ t calibration. An in-flight

cal ibration system, the first of its kind, has been

de vel op ed by NA SA to track SS BU V ins trument

response from the time it leaves the laboratory until

the time it returns. An srrsy of halogen, deuter ium,

an d mercury la mps provides a stable UV light source,

an d performs on-board wa vel en gt h and radiometric

calibration checks. These lamps are activated by

command of the Mission Specialist.

A special Calibration Facility has been set up at

GS FC to dev elop an d test the SS BU V instrument

and maintain a state-of-the-art calibration

capability (see flow diagram below). This facility

contains all the necessary test equipment toperform accurate and precise calibrations of the

instrument for the duration of the experiment. A

refurbished Nimbus-7 SBUV Engineering Model

wil l be use d as a laboratory reference instrument

by tracking the radiometric standards and

calibration of the flight instrument. Laboratory

intercomparisons will be performed with other

solar-ultraviolet radiation-measuring instruments

to be flown on the Shuttle and UARS.

SPACE FLIGHT

SSBUV

Flow diagram of the SSBUV calibration

before, during, and after the SSBUV flight.

The process involves pre- and post-flight

calibrations against a laboratory instru

ment and radiometric standards de

veloped by the National Institute ofStan

dards and Technology (NIST, formerly the

National Bureau of Standards). On-board

calibration checks are conducted by the

SSBUV's own calibration system.

IN-FLIGHTCALIBRATIONS
http://n-orb/thttp://n-orb/thttp://n-orb/t


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Mission Requirements.The first S S B U V flight wil l oc cu r in late 1989, wi t h

regular flights scheduled throughout the 1990s.

Mission requirements with respect to data collection

are:

Shuttle f l ights every 8-12 months coincident with

N O A A SB UV /2 instru ment ope ra t i on unt i l 1996

Solar view data at least twice per Shuttle mission

Earth v i e w data of suffic ient dura t io n to c o m p a r e w i t h

SBUV/2 . This translates to 32 co inc ide nt me as ur em en ts

with SSBUV and SBUV/2 instruments , equivalent to

a b o u t 16 hou rs of Ea rth obs erv at io ns

SSBUV Benefits and Applications...

Implementation of the SSBUV program represents a

major step forward in our ability to e nh an ce the

reliability an d integrity of the long-term e nv i ronmen

tal data sets obtained through space-based

remote-sensing instruments. Regular observations

by the SSBUV instrument on board the Shuttle also

wi l l :

Provide more accurate, re l iable readings of global

ozone , result ing in better de te rm in at io n of trends a n d

a surer basis for protective actions

En ab le the de ve lo pm en t o f impr ove d mod e ls o f ozo ne

dynami c s , al l ow in g a bet ter und ers tan din g of oz on e

change and i ts causes

Serve as an impetus to the development of

spa ce- bas ed ap pr oa ch es to preve nt ing or mit igat ing

the effects of instrument degradat ion

For more information on the SSBUV program, contact:

Ernest Hilsenrath, SSBUV Principal Investigator,

Goddard Space Flight Center, Greenbelt, Maryland 20771,

or

Robert Watson, Chief, Upper Atmosphere Research

Program, NASA Headquarters, Washington, D.C 20546

Documents

The Shuttle Black Scatter Ultraviolet Experiment Pamphlet