SUMER: Solar Ultraviolet Measurements of Emitted Radiation

6 33 31

N90-13307

'SUMER'

-

K. Wilhelm

SOLAR

1, W.I.

ULTRAVIOLET

Axford 1, W. Curdt

E. Marsch

_, A.I.

1, A.H.

Poland

s, A.K.

I Max-Planck-Institut 3 Astronomisches

Institut,

Tfibingen;

5 NASA/Goddard

Gabriel

2, M. Grewing

Richter

I , R.J.

ffir Aeronomie;

4 Space

Space

MEASUREMENTS

Science

Flight

Center;

s Center

ABSTRACT SUMER

diation

-

- Solar

we

will

Ultraviolet

study

netic

activity

scales.

will

This

be

on

to the

a A]_A of up size. Spectral

and time. its spectral

to 4.0 × shifts c_a

wavelength

range

gration

time

on line

profiles,

can

Keywords: celeration.

for

Space

planets,

from

as ls.

and

emission

inte-

as on

ratios

heating,

solar

of

that

are

wind

ac-

SCIENTIFIC

spectral many

density

fields,

and

topologies dynamics.

• Solar

of the

areas

physics.

source

• Stellar physical angular where

abundances

plasma

are

between

of the local regions

will

Coronal

and

density

ded

more

loops

evolution

importance

Many

coronal

for

stars is crucial

wind

be tested

mechanisms.

will give

and

have

is essential

heating

distribution its

to our

insights

into

and

winds.

understanding

Their of stellar

The Sun is the only star heating and wind genera-

observationally

and

topology

of the

by resolving

solar

plasma

is defined

tailed

offers

understanding

• Solar-terrestrial

the long-sought

of astrophysical relationship.

and The

opportunity laboratory

Earth,

to improve plasmas.

in common

solar

wind

and

radiation

dynamically

field.

to photons

and

Solar

Transition

Region

and

which

to values

The

with

outer

as a function

of height,

features, points.

from

such In

values

occupies

in excess

solar

these

within

which the

above

corona,

are embedprominences,

K in the

2 x 103 km

of 10 _ K in the

often

temperature

regions,

descriptions 104

has

where

as active

of about

the first

atmosphere

background,

temperature

chromospheric

the photosphere,

across

a transition

re-

gion only a few hundred kilometres thick. One would, however, expect a temperature decrease with distance from the photosphere tence

unless non-radiative of a chromosphere

and

heating takes place. a corona requires

ergy input to compensate for for the solar wind expansion.

presence

radiative The

Thus, the a persistent

exisen-

and conductive losses and relative importance of the

to be responsible for this energy input is a However, as pointed out by Athay (Ref. 1),

of any

non-radiative

should

manifest

itself

optical

means

in terms

mechanical

by fluctuations, of line

heating

which

may

broadenings

and

mechanism

be detected Doppler

by

shifts.

Solar

wind

mechanism

acceleration.

proposed

by

The

Parker

thermal-pressure

(Ref.

2),

gradient

is inadequate

to

ac-

celerate the solar wind to the high velocities observed in streams associated with coronal holes and may even be inadequate for the

current

solar

picture

mechanisms measured

at

wind

of the

(ttef. 3-6) a distance

concepts

of high

amount

of wave

by wave

pressure

over

solar

solar

available

gradient

of the

Sun.

further

the properties 0.3 AU from wind

corona

although

our

that have been the Sun. Modhinge

to drive

it is also

accumulated

Thus,

acceleration

acceleration

in the

forces,

the solar wind represents the isolated acceleration sites.

rest demands

to explain beyond

speed

energy

the

wind

effect

on the

the wind

possible of many

that small

the

which are rooted in the photosphere and connatural plasma environment accessible to de-

observations

in the

plasma

bright

layer,

1.2.3 The

Zfirich;

Sun.

heating.

vary

abruptly

ern

acceleration.

coronae

loss and evolution. concepts of coronal may

parameters

the

as a quiet

complex

rises

1.2.2

velocity

by magnetic fields, vection zone. This our

in the responds

from

Astronomie, Stanford

allow

atmosphere:

time

ffir

atmosphere

described

producing

different

energy

interpretation

mechanisms

their of prime

of these

of the solar

physics.

plasma structures. • Plasma physics.

lines

solar

of species,

structures,

measurements

A determination

momentum theoretical

emission of the

of science:

for discriminating Knowledge

in EUV

parameters

temperature,

Such

following

imaging

physical

Institut

is immersed

expelled

2,

Vial 2

Astrophysics,

Ph_'sical Processes Low Corona

been

the

OBJECTIVES

Perspective

plasma

tion

will in

The

emission lines 2 x 10SK.

coronal

and

terrestrial

1.2.1

heat-

will be obtained

as well

EUV 104 and

lines,

to 1600/_.

Information

broadenings,

Jordan s, P. Lemaire J.-C.

temporal

a spatial resolution is characterized by

500

RADIATION

Spatiale; and

Science

particles

1.2

4, S.D. s, and

d'Astrophysique

processes proposed matter of debate.

us to study

tile

and

of coronal

104, where $_, corresponds to the pixel be determined with sub-pixel accuracy.

be as short

EUV

High-accuracy

the

tem-

spatial

It can provide resolving power

will extend

shifts

1.

and

various

understanding

temperatureand density-sensitive formed at temperatures between

1.1

waves,

upper atmosphere with solar mag-

and the solar wind expansion. The instrument of the Sun in EUV light with high resolution

space, wavelength of 1.2 arcsec and

The

observed

Ra-

motions,

of the plasma in the and events associated

will contribute

ing processes take images

turbulent

of Emitted

ttuber

Timothy

of ESA/ESTEC

other

Measurements

flows,

peratures and densities of the Sun. Structures

5, J.G.

2 Institut

The With

3, M.C.E.

Thomas

Department

OF EMIfrED

the

Structure

the corona small state of fluctuation and

sometimes

plays a dominant conditions seen field

may

of the

solar

and large on time weeks.

upper

By confining

rSle in permitting in coronal structures.

be responsible

atmosphere.

inhomogeneities scales ranging

for both

plasma,

At

the

base

of

are in a continuous from seconds to days the

magnetic

field

the large variety of physical In addition, the magnetic

transporting

and

dissipating

the

32

K.

energy

needed

In fact,

although

spheric

levels

the

to maintain in quiet

same

(Refs.

dominantly

into

used

the

plasma

the non-thermal regions

7, 8),

the

heat

the

holes

non-thermal former

solar

energy

case,

whilst

&AL

atmosphere.

temperatures.

flux supplied

and coronal

in the

in accelerating

at coronal

energy

WILHELM

may

at chromo-

be

actual

turbulence.

is converted

pre-

• Line

pair

in the latter

it is

species

wind.

T,

the

Required

In order to understand

must

the budget

understand

and

of the solar wind, we

transfer of mass, momentum

and energy in the differentstructures of the chromosphere,

tran-

sition region and lower corona. Therefore, we need to examine flows, oscillationsand transient events and, at the same time, to investigate the plasma ture distribution. We

density, emission measure

plan to study solar structures down

1600 ._ covered by SUMER. at

shorter

Some

and

tempera-

to the 1-arcsec level with

the help of emission lines in the wavelength

range are shown

range from 500 to

of the linesobservable in this

in Fig. 1. This coverage has to be complemented

wavelengths

by

electron

ratio

the

Coronal

Diagnostic

Spectrometer

metastable

level

levels

termined

by

Performance

The

SUMER

instrument

with

a collecting

,

7

_--=7

I st

2 nd order SUMER

order

limit,

Fe_•m•Fex Si_

o$

Ne_

h

N'_

The

effective

lated

from area

tivities,

and

w

Fig.

and

parabolic

dif-

largely

de-

is encircled

In

in 0.5 arcsec. will

pro-

detectors with high areas on the Sun.

optics

res-

range

in order

continuum

mirror

telescope.

normal-incidence

selected

intense

s_

a spectral

equivalent =

from

500 to 1600

to include

radiation.

of the

surface

telescope,

E 9, Ed

are

the

The

,/_.

C IV

lower

limit

of 40 _ in 1st order

of the

instrument

we obtain

and

reflectance

grating

the to

effective

MgF2

and

in the

spatial

be calcu-

mirror

reflec-

efficiencies

(Ref.

12) for

be half

collecting

0.8 cm 2 for

and

collecting

detector

of SiC

efficiency

a maximum

crn 2 for

can

S is the

Rp2, R_,n are the

grating

the

the

where

Rpl,

the

If we use

0.3

range

SRplRp2R,,_EgEd,

assume

proximately

the area

KBr

all

mirror of ap-

detector

coatings. The

L 600

the

is of the order density, when

off-axis

the wavelength

was

observes order.

3).

mirrors refiectivlty,

10 500

T when

are

on 2-dimensional profiles for small

covers

Ax

surface

(cf.

NI3/.

I0S

of

excited

populations

a single

using

to avoid

ratio

9-11).

80 % of the energy

boundary

simultaneously 20/_ in 2nd

Fex'ff_ • Fe'X'II • • SiX w"

but

The

transitions

was set by the normal-incidence technique employed. The range from 500 to 800 Jt will be observed in the 2nd order spectrum, whilst 800 to 1600 _t can be scanned in 1st order. The instrument

SUMER

I07 1

lines,

pairs.

of S = 117 cm 2 as the primary

A grating-spectrometer

upper

line

measurements

Characteristics

vide stigmatic spectra olution to resolve line

The

temperature

from

on temperature

uses

area

or by

of highly-ionized

electron

allowed

(whose

widths

activity

of the two transitions dependent on dectron

(Refs.

SUMER

thermal

wave

source

selected

are involved

1.4

the

the

of the

is dependent

collisions)

the diffraction

either

optically-thin,

between the energies Ratios also become

The spectrometer

- CDS.

N,

of

and/or

of excitation

on

of certain

for two

the same

ference of kT.

physics

density

intensity

from

the global balance of the inhomogeneous

including the dynamics

Atomic

excess

flows

information

the emissivities

solar atmosphere,

in

unresolved

ratios.

provides

or

broadening

by

is approximately

of the 1.3 Measurements

Line caused

I

I

.d

+

1

i

[

700

800

900

1000

1100

1200

1300

I

pixel

size

of 25 pm

direction

corresponds

to

I

_

ISO0

an

1600

angular

Sun.

element

The

of 1 arcsec

spatial

resolution

or

thus

a distance achieved

of

700

km

is adequate

on

the

to study

Wavelength,

small-scale Fig.

I

range

Selection

from

500

of emission to

lines

in

the

SUMER

with used

wavelength

1600/_

desired

temporal

transient

events.

A wider

case

may

and

some but

other

require

activity

sampling

as welt

does

time

network

not

and its as for

the

decay

times

structures

a better

quences should no interruptions.

these picture

by the + Line give

following profiles,

information

such

This

is the

into

tile

lifetimes most

case for Corona,

reconnection

the

centres

and

loop

different

wavelengths

Sun.

is an excellent

platform

of

slit

Ideally

from

growth

of

be

20.5

to make

m,_.,

spectral

and

about

the

dynamical

These

measurements

phenomena

in

the

will solar

permit

to the The

a pixel detected

a plate

obserof a sin-

in regions

scale

between

and double

with

0.59

those

and

values

A/6A characterizing

between

observing

1.9 x

wavelength,

line

of a line width,

the

By using

tistical function

noise, we obtain the of the total number cases The

Doppler

off-the-limb

boundaries. The length of aresec. The spectral res-

parameter

varies

length.

the

for

slit widths 1.0 arcsec.

characteristics

observations

spectrum

The

sensitivity the

three

is compatible

in

104 and

where

the

4.0

xl04

6A corresponds

size.

velocity

width.

and

size of 25 #m in the diffraction direction, spectral elements of _iA _ 41 m/k and

power

of the

pixel

by

1st order

respectively.

as a function

for broadenings.

be selected

low-scattering

characterized

resolving

of counts,

techniques:

can

The

will also

in the

and

The physical properties of the solar atmoand regions discussed above can be determined

shifts

can

mm/_

tor-

se-

4 arcsec

telescope

structures

strong gradients, such as coronal hole the slits will be between 25 and 300

2nd order. With we thus obtain

of time with orbit around which

with

and other

of the spacecraft stability. The on the solar disk will be 0.5 or

to 1.5 R®.

gle mirror

0.63

would

observing

out

olution

chromo-

for

and

of the varying

study

time resolution

periodicities, at

of the

demanding

1 s. The

a high

be performed over extended periods For this reason SOHO in its halo

the L1 libration point such observations.

1.3.1 Techniques. spheric structures

the

of about

need

large-scale

of lifetimes,

provide

times

extension

Measurements

on the

represents

coverage.

sions.

of

depends

activity

phenomena

a continuous

spheric

resolution

Wave

loops

the design goal for observations

vations The

coronal

a Gaussian

plotted

in

velocity

was

formula

vi =

is a function spectra]

line

profile,

expected of counts. Fig.

2,

c(A -

only

Ao)/Ao,

total

and

Doppler

wavelength

where

waveby sta-

sensitivity as a been estimated

AA D is the the

number

the

perturbed

line shift This has

where

derived.from

of the

element

A• is the

shift

by

nomi-

UV

nal

wavelength

the

sensitivity.

to

about

of a line. We

1 to 3 km/s

features

on

to 3 s can

be

step and

one

from 10 s.

noise

for

with

at sub-pixel

Depending

Other

expect

MEASUREMENTS

sources

many

will also

lines

a position

a useful

OF

influence

range

determination

intensity,

obtained.

The

wavelength

a temporal

of spectral

time

resolution

required

range

to the

for

next

down

to

1

the instrument

would

RADIATION

characteristics

down

accuracy.

the line

EMITTED

to

be between

1

,

solar

enhanced vations

made

I

A),o= 100

21.5

determinations.

[

A),Q=200 A;_o=t00

21,5 ,3

provide

_m/s(a,1500_,

]

3

One of the observations

_

..

g

1000

Fig. 2 SUMER

Diagram showing the expected as a function of the total number

velocity sensitivity of counts in a line

different

sets

Lines

the

for

Dynamic

will primarily

radiation

with

atmosphere

from

the scan

and

Diagnostic

determine

the aim

of for

standard

co-ordinate

the

mirror

characteristics

i:

or ions.

It is thus

essential

A particularly to SUMER

shown

pattern

on

in Table

the

of the solar

the

fieldsimul-

understanding

will

thus

be

greatly

related

obser-

with

the

Diagnostic

Spectrom-

instrument

extends

our

providing the opportunity for density and temperature pair,

range

for instance,

from

prime

only

to

that

can

3 x l0 s to 1 × l0 s K,

window

be observed

of SUMER by grazing

details

lines

for

dynamical

scan position 1st order and

studies

observable

still

at

corresponding to a range from 609-629 _. in 2nd order. Count

has

whilst incidence

for the

full line

and

a spatial

resolution

Wave- ]t length,

Te,K

cathode

C I

1.0

x

104

1253.40

15

95

KBr

N V

1.5

x 10 s

72

Fe XII

1.8

x

106

1242.80 1242.00

942 255

KBr KBr

N V

1.5

x 105

1238.82

39

179

MgFz

0

2.5

x

l0 s

1.1

x

106

1218.35 625.20

3 5

33 38

MgF2 KBr

V

Mg X

609.80

2 shows

a selection

or temperature ratios

are useful,

imum

abundance.

of predicted

pairs

The

density

are indicated, The

count

a scan

as are

intensities

rates,

be observed

are

of

also

using

mirror

7

of line

dependent.

the

motion

48

whose the

definition restricted studies,

and by as well. periods

The

lines,

with

Many

scan

pairs

mirror

in

to

perform

a

technique

Spectrometer erated flow Light

diagnostics

a corresponding

scientific approach generation

CORRELATIVE objectives in

the

processes.

STUDIES

outlined study

in of

the

terms Some

SUMER

coronal has

very

hope

deadtime.

charge

state

DATA data

obtained

rate

of SOHO

that

the

time

of 2 years.

lines

above with

not

original

wind

full

dump on in-

instrument using

allows

the

Doppler

Ultraviolet

would

solar

Coronal

density

experiments

solar

plasma

at

and

the

composition

as determined

System

by

the

Charge,

- CELIAS.

AND

ANALYSIS and

PLAN

reduction

The

these

would

the

particle

of the be the

ions

requires

provide

wind

experiment.

rate

of the

instruments.

as the

compression

only data

the

analysis.

would

Analysis

of this

For

slot, a data information

by

characteristics

selection,

which on

activities

analysis

REDUCTION

aspect

within

lower heights. The onset of accelcorona can thus be studied. The

interest

Isotope

on

be interpreted.

other

LASCO

the

of the solar

and

SUMER

provides

spatial ment

extent.

methods

limited

schemes,

give 2 x 10

In parallel

and

ciate

high

performance

data

and

in more

displayed

than

as images coded with

scientists analysis

high

spectral

distributions

Temperature

a co-ordisolar

spectroheliograms The

of spatial

fields.

parameters for

-

for

in-situ

Of particular

heating

1 call

the

and

same

to co-operate

measure

observing

PLAN

Section

to

in the SUMEK

but at of the

Coronagraph necessary

1 AU.

and 2.

CDS

for the

areas

is also necessary

conditions

imaging

velocity

- UVCS, at the base

inEIT

Doppler ImagerMDI will be reteam will use the long non-station

light

a radial

lead

Telescope-

observations

to perform

of scattered

also

real-time

appropriate

have

a

but bits

TM

are

transmission also over

the

fact

a mission

the

can simul-

setting.

Imaging

boundary

magnetograph

will

information

observations

for SUMER,

level

an essential

of max-

given

of the

to

by all experiments.

or near

selecting

This

the Michelson The SUMER

areas

low

On-board

density

for

camera to de'he

of SUMER

Ultraviolet

angle

a Sun

will be used

in real-time

corona.

of SOttO

3.

which

temperatures

shown. same

axe

over

view inner

spatially

Element

MgF2

ratios

ranges,

these

a wider

have

be important

field-of.view

Eztreme

a proper

that

Counts/s[PhotoQuiet [ Plage

the

the

We also Atom[Temperaor Ion ture,

that

in co-ordinating the in space and time is

will

It will also

system

for

White rates expected are given element of 1 arcsec 2.

SUMER

of receiving

from

teresting

implies

of which

has to be solved one instrument

solar disk. At the beginning of an acquisition followed by a quicklook display could provide

good coverage can be obtained table

that than

instantaneous

the Sun or in the

pass

to determine

1. The

detector,

which

us

Selected

single wavelength 1218-1258 k in

wind

This

an alignment.

requirement

ground quired

of emitted

parameters

position

narrow

dimming Table

nated

into

co-alignment.

magnetic

Studies

plasma

and line pairs. range accessible

a specific coating have to be studied.

The

falls

such

formation

of deriving

atoms

appropriate lines of the temperature

require

Coronal

wide

at 173 _ can

problems of more

relative

to the

of parameters.

SUMER

taneously

the

O VI ion line

in the

facilitate

The 100 Total numberof Counts

Table

For the

one

to

way.

to shorter values, line ratio pairs

at 1032/_.

a restricted

techniques.

111

at

close

temperatures

line

dynamics

measurements

with

a very

SUMER

for

small intrinsic can be covered

or elsewhere.

to co-operate in

of its

its

on SOHO

- CDS

one

and

by co-ordinating

the other

1.5

contribution

atmosphere

Linewidth,m_

._

resolution

The

of the

wavelength range measure additional

3km/s(at 1500 _}

spectral

taneously.

_ .-T-,,Pixel,m_

30

and

range. This implies a relatively a narrow spectral window that

eter _

in spatial

wavelength of-view and

We plan

100!

33

one

tasks,

line.

plasma

lines

velocity

distributions All

of variable

the measureand

turbulence

can be obtained

of these

of 2-dimensional

and

permits

data

arrays

with

can

by

be stored

the relevant

appropriately.

the real-time and

of

density

in many resolution

data

evaluation,

guest

investigators

using

the capabilities

will

investigators, perform

provided

asso-

preliminazy by the Exper-

34

K. WILHELM&AL

Table

2:

Selected

are given

for the

line pairs full line

useful

and

Ion

or temperature

resolution

1213/1196

C Ill

1176/977

7.0 X 104

1.0 x 101°

2.5 x l0 s

1312/1301

1.0 x 109 -

1.0 x 1011

3.5 x 104 8.0x

N III

991/686

i

3

iment

Schematic

but

shown

Operations from

design is the

Facility

the

also

prepare

baffle

optical

Also

co-ordinate

Optical

data

(pl]

(EOF).

collected

0

69/9

5

46/5

203/7

4

334/*

1730/*

- CDS

observations

stop

Detector

only

for

scan

SOHO

mirror

team

will

experiments,

observations

future

and

the

assembly

detectors

have

4.1

The

The

main

tain

high

and

the

lowed

TECHNICAL

SUMER

and

will

operations.

in the

spectrometer

One

of the

main

detection

objective

of the

spectral inner

and

An

spatial favours

by a spectrometer

using

requirements,

furthermore,

the

of the

incidence

the same

drive

namely

images

a normal

to ob-

solar

disk

telescope

technique. design

High

fol-

contrast

to a single

off-axis

primary telescope mirror with low light scattering characteristics. This eliminates at the same time solar flux concentrations on

a secondary

mirror

tial sensitivity carbide and than

for the %

The

telescope motion thus

operational

the

danger

of

substrate

in terms thermal

of optical

properties.

wavelength

mirror

can

required the

provides

silicon

appears

to be

quality,

UV

Its

range

perform about

to achieve

instrument great

constraints.

poten-

Chemical-wpour-deposited a SiC

of =t: 30 arcmin

us to mount and

the

reduces

from

both two

reflectance 600

to

in a fixed simplifications This

scheme,

the

of the position

has

and

we selected

a design

that

leads

camern

drawn

in the

extreme

This the

allows as in

path

the

detector

and

launch

design, cluded.

positions

The

of their

detector

and

with

mass

storage

and

power

requirements

respectively

(89.2

Interface

under

be

study

devices.

kg and

in order

to

assembly

of

ground

of identical inand,

requirements

supported

Part and

by image

processors and

data

B).

mem-

be partially

handling

schemes

The

are 91

low

the

will

period.

are agreed

optimize

part

handling

data

35 W EID

for

seal during

and

operation

High

be an unaccept-

required

deteriorated

instrument

kbit/s.

the

a slightly

of the

Document, 10.5

its

to

and seM, was therefore at longer wavelengths

control

the SUMER

and

led

position,

The

to implement during

would

detector

2 to 3 transputers

evolve

will

control

as it fulfils

of SUMER

coating

not

(Multi-Anode

detector

by a hermetic

mounting

yet should

of the detector

assembly KBr

A second

experiment

and

the prime

operation

as the

off-axis

on-board

total

k9 and

mass 37

W,

with

ESA in the Exper-

The

nominal

bitrate

telemetry

modes

telemetry

are

also

requirements

of

experiments. instrumentation

to

any

cleanliness SUMEK of

the

stop.

lies in an efficient

a MAMA

complexity

to be protected

that

EUV

for

aperture

range device

but without sensitive coating It would have less sensitivity

led to a design

rate

for

The

operations.

EUV

We selected

detector

a single

has

a well-defined

to be an open

light.

in particular,

because of its resolution.

tive

the disadvan-

to a constant

risk,

several

spacecra.ft

as well

that

able

with

It has

importance

conclusion

iment

the

tage that the path of rays inside the instrument is not constant for different viewing directions. In order to minimize calibration complexity,

Sun

baffle

requirements.

reprogrammable

,_, with

pointing

Sun.

in the design however,

Optical

in our

Array)

of our

ories

suitable for continuum.

axes on

best

is greater

2000

instrument

perpendicular

images

the

reflectivity

of 50 % near 1600 ._ and is, therefore, above 500 ,_ and below the intense solar

in a range scan

and

in

a maximum observations

on

optics

mechanical 40

thus

deteriorations.

- SiC(CVD)

material

and

Rear

area

to visible

paramount

measurements,

resolution

corona,

most

Overview

SUMER

A

camera

difficulties

system.

be sensitive

DESC1LIPTION

_strument:

been

rays

Microchannel 4.

Detector

system.

analysis

from

ground-based

requirements

The

B

,

Slit

co-ordinate

A science

not

simultaneous

scientific

of SUMER.

experiment

0

42/6

!

mirror

3

105

10e

s

2

104-2.0x

Aperture

Telescope

time, 0

38/69

Spectrometer

(pm)

Plage

5/11

s-l.Ox

photocathode variations.

Dead.

1

106

/p

-- ÷XE

ranges.

mirror

Diagnostic

a KBr range

s-l.5x

3.0X10 * Coronal

using

9/2 46/16 178/305 1950/20T0 7/52 2O/lOO -/7 31/85

< 7.0 x 10 4

1032/173

rates

for wavelength

Counts/6

1.0 x 101°

790/554

count

Network

1.0 x 109 -

VI

expected are required

To, K 1.2 x l0 s

1.0 x 109-

X

Scan

The

times

Temperature

Ne, electrons/cm 3 2.0 x 108 - 2.0 x 101°

O IV

Grating{g]

studies. 2. Dead

3.0xlO

0

scan

1 arcsec

625/609

Mg

Fig.

diagnostic of

760/630

V

Si III

element Density

Wavelength,

S X

0

for density

a spatial

spectrometer

type

exposed of

programme product will

to the

chemical

or

will

thus

full solar

particulate be

a major

assurance

activities.

be

in a tight

housed

flux is very

sensi-

contamination. The

case

effort telescope (that

A

within

would

the

and

the

at

the

UV

same

MEASUREMENTS

time serve as optical bench) and

in the design. There

a door will be included

will stillbe the need for nitrogen purging,

as it will be impossible to develop a vacuum-tight the given mass

constraints. SUMER

sumables, and a certain limit its the

consequently

microchannel

plate We

safe life of these we will allocate the

first

year

on

Optical

of

paral]el concave on

images

slit

range

of the

full spectral

beam

parabola issued

from

selected The

focus.

image eter.

The

allow

for

and

the

iments

whilst

The

effective

(0.5

arcsec),

corona resolution the

slit For

achieve

bration

of the

ity

made solar can

justment

by observing

limb also

The

plane

the

grating,

detection

and

the

a linear

The

is given

by

An = nm

solar

adjustment i)/m,

where

is the grating

features by

angle

of i on

m is the

focal

grating

normal

observing

for a 3600

order

grooves/ram

4.2.2 Focal plane has a focal distance varying

with

wavelength

800 _. to 1760 focal factors

length

mm

of the

of 4.1

is stigmatic 43 m,_ and

design. The and a plate and

from 0.63

collimator

to 4.4

in the

grating factor about

mm/]_

with a radius r = 3.2 m in the first order spectrum 1640

at

of 0.4 m, spatial

within a large field. 0.5 arcsec in the 40-_

mm

1600

and

,_. Together

we obtain

domain.

0.59 mm/_,

The

with

at the

magnification configuration

The resolution is better x 300-arcsec field chosen

than in the

the

motor.

In case

pointing.

the optical will not slit),

tred

on

slit

This

spherical

be

but (R

motion

tilted

guided

by its ends

circ_Jar

motion

with

when

By ray

tan

(a/2)

Electronics

whilst

the other

processors,

processing.

They

emergency

The

perform

both

cessors

could

The

operating

kept

alive

will partly

its

is read with

the

Experiment Unit

are

mode

(4-0.5

where/_

own tasks

also be interchanged memories

of both

by a constantly

powered

be adjustable

The

is the slit

are

ECP

return

evaluation within

with the

a view

fixed

to enhancing

telemetry

and data

This

other

failure

allows could

The

SPU

will be They

via ground

The

pro-

modes.

the spacecraft.

the science

allocation.

in

and

processor

the

in

memdetector

(ECP)

mand sequences. Programme changes of the on-board will be made on the basis of actual data received and ence

than

results

one.

changes

the

dimension.

other and

from

of

that

for control each

in certain

by programme

A

transferred

Processm:

of the

line

a.

length

a spectral

where

the

a tilt

is better

interchangeable. those

cir-

and

accumulation

and

axe used

selected and

the

be shown

data

Control

functionally to be

of two

deg),

It has two independent for accumulating the

out.

cen-

mirror).

willapproximately

detector

(SPU),

paraboloid

set at an angle

it can

a spatial

to the

surface

a displacement

= L/(2R),

memory. is used

the

superposition

of rails

com-

slit,

as the

of curwture/Z

image

Processing

In order

move

spectrometer entrance 1 × ldeg 2 raster range.

digital format to an image ory planes, one of which

will

scan.

of off-axis

computations,

The of this

length

by

to

system

a spherical

angles

on a pair

a radius

tracing

a 2-dimensional

on

be approximated

of

has

aperture.

on the entrance

would

For small

risk

by a pyrotechnical

raster

(which

focal

the design

door.

around

is implemented

motions.

can

mirror

detail.

of ran/function

the

of the image

moved

of a bar

Signal

the

oper-

in some

entrance

the high-resolution

= apparent

circular

for the

here

is released with

The

and

quality

only

off the

motion

frame

together

pointing

axis

an

grating.

of opening

annular back

Telescope

Two

for

aluminium.

will be required

its

way

rotated

the coarse

the

struc-

housing

carries

by a stepper

the underlying

output

reand

The

bare

instrument,

system.

high

and

will be

mechanism

4.2.5

a rotation

effects.

bench

housing

4.

surface

contamination

this

the the

ad-

avoids

in Fig.

inner

whole

image quality on 0.5 arcsec within

slit

as shown

metallic

Since of the

a redundant

bar.

optical the

to the multicomponents

described

door. failure

is opened

the

positioned

are

qual-

of incidence the

point

be achieved

l_lane

with

Entrance

a single

mirror

be

of them

the

focus

monochromatic

onto

constant

focal

4.2.4-1

4.2.4-2

secondary

These components substructures con-

outgassing

Six mechanisms Two

Calithe

optimal

out

of the

diffracted

The

the

or other the

0.5 arcsec

behind

light.

is carried

modifying

We ob-

of the image

located on

limb

scan

the

Mechanisms. of SUMER.

and

the of

a

The will

section

and

by

with

mirror.

ation

cular

observing

as

inside

primary

device

optics

and

to the spacecraft is via thermally isolating isostatic instrument carries a radiator of 1400 cm 2 for cool-

4.2.4

drive,

It

on

detector

direction.

smooth

caused

both The

The interface mounts. ;the the

operations.

spacer and

EUV

deformation

is utilized

ing

a clean

prime

it requires

of telescope and spectrometer. Due of rays in the instrument, the optical

by the sensitive

instrument.

of this portion

dispersion

lightweight

distance

The

(MCP)

coating.

in the

7-era

Consequently

launch

a MgF2

axis

presents

structural

range.

and along

will be positioned

towards its front and rear ends. be mounted inside two box-like

orthogonal

quality

of 1.2 arcsec.

checks

in diffracted

wavelength (dsin

and

image

use

disk

directions.

arc_ec).

we can

to

solar

all

quired

pixels

short-wavelength

and

have

by a stiffbut

maintain

SUMER

of the

(_0.5

resolution

information

thereby

fx.

for most

lines,

only

at

direction.

plate

with

of 2.5 arcsec

be obtained

× 1024

its

for ground grating

design

bine

enough

the

in

of the

of a camera

wavelength

mirror,

d = 278

help

P_

jitter

spatial

or

corona/exper-

to scan 1.5

arcsec

bright

provide

distance and

(1

within around

arcsec

between

nected

in

combines tangential

resolution

microchannel

MgF2

curvature

corresponding

dispersion

long-wavelength

will

image

will

the

of 360

The

with

7 cm off the

This

in

a field

axis.

detector

door

high-angular

is large

convolution

mechanism

the

the

the other

least

pointing

pointing

detector

the

width very

with

at

is the

an effective

through

contrast.

the grating

the

on the

An angular

axis

having

include

coverage

slit of the "spectrom-

capability

to

the spacecraft

1.5 arcsec.

are

the out

and

the

a wavelength

of 0.76

achieved

reference

of the

to any target by a rotation

of misalignments

optical

the slit

limits

The

requires

in steps

thus

range

direction

the entrance

field-of-view

The

detec-

characteristics

compromising

on

maintaining

inner

and

slit and

without

slit.

a spherical

collects slit. The

simultaneously.

accomplished

compensation

spacecraft

the

tain

be

arcsec

actual

the onto

wavelength

diffraction

of the instrument

of 0.5 arcsec

some

and

modes)

can

of 0.38

quality

detector

ture

a focal

2-dimensional

the spatial

can be observed range

This

steps

spectrometer

plane of the concave grating of the spectrometer entrance size in the

made mirror

having

mirror

The telescope mirror can be directed 1- deg _ solid angle centred at the Sun

half

all

as telescope

scan

the

determine

that

grating,

mir-

loci

slit image

grating

4.2.3 Structure pie-folded path

3 is baaed

parabolic

Sun on the

mount).

substan-

in Fig.

off-a_ds

an off-axis

the

will

shown

the

to the

field,

two

surfaces.

are grouped can therefore

parabola

diffracts

detector

spectral

a quarter

concave

off-axis

by a plane

the focal images

therefore

than

two

a spherical

the

which

the

its

and

(Wadsworth

images

scan. a lx

design

components:

of 1.3-m

dimensions and

optical

The

is deflected

tor located in monochromatic

more

Instrument

m collimates

normal

not

of the

A 4.50

grating,

its

the

35

this

monochromatic

from

is coated

duration

planning of the observations on critical items.

Behind

0.4

of the various

the

the

focal

assembly

and

for

sagittal

to give

door

length

beam

times

limits

tb.at may counts of

Outside

devices in space. On the basis of these numbers, not more than half of the available resources to

mirror

slit.

the run

upper

to

order.

astigmatism

in the

optical

a focM

entrance length

limited

first

RADIATION

KBr

of SiC(CVD).

with

not

EMITTED

of

design.

a plane

out

is in principle

and

establish

Description

well-known

rors,

detectors

will

Careful the load

Detailed

4.2.1

will not contain any con-

its life

of operation

second year. tially reduce

4.2

system within

time span. There are, however, a few aspects effective life. These axe the total number of

mechanisms.

OF

com-

software on the sciinformation

mass

memory

36

K. WILHELM

&AL

_35

Sun

[omero

Opt.reLmirror

Opt.ref.mirro_

RodiQtor

.zoo

"ZE

Aperture door

• COG S Mirror

__--_ Ntg. pt

_"_

_perture

Temperature reference point / Connectors\

,I__

VG_ Purge V_tEX

Aplrture_idoor Opt.ref.mirror

\

i_'_®/

•

__ u_bstructe_

Radiato.,"_

Fig.

4

Mechanical

design

the centre of the slit. locations of the centre will mainly and

for

be used

for storing

short-term

controlled

1 and

definition

data

during

on-board

operations.

All

calculations

mechanisms

the

instrument

will

be

essential

in terms of quantitative calibration is needed

transfer

function,

and

to

in-

scientific paof the relative

relative

the absothe instru-

and

absolute

wavelength conversions. rive the heat input and

Absolute intensities are required to dethe radiative loss rate that maintain the

transition

corona.

and

the

The

to be repeated periodically during tect possible in-flight variations. Intercalibration length

with

range

will

intercalibration tained ing

be an

by both

the

minating spacecraft has

to

be initaJ

For

the

dedicated

AND

SCIENCE

of SOHO

on

pointed

towards

approximately

its

way

configuration,

campaigns. calls

for

an

of standardized

centre

Associate

including The

programmes

wave-

CDS/SUMER line

ratios

rocket

to

the

Sun

to the

solar

standard

operational and

obdur-

plan

orbit

a stable XE-axis its

dan,

G. Doschek, R.A. Lfihe,

an efficient

system The

hal,

D.

B.E.

Samain,

will

be in

approximate

Tondello,

gether

J.

with

Mason, E.R. V.M.

Advisory Group implementation

M.

J.L.

P. GoutteC. Jor-

Leroy,

I. Liede,

McWhirter,

P. Mein,

H. Rosenbauer, Schlissler

Vasyliunas,

define

Delabou-

K. Jockers,

R.W.P. Priest,

Schmitt,

Investigators,

Ip,

B. Leroy,

H.E.

F. Bely-

J.P.

B. Foing,

W.-H.

Patchett,

Triimper,

the

Barnstedt,

Cuihane,

G. Einaudi,

Haupt,

J.H.M.M.

J.

J.L.

F. Kneer,

P. Maltby,

Parkinson,

G.

H.F.

O. Kjeldseth-Moe,

O.v.d.

Cruise,

J. Dubau,

Harrison,

J.H.

O.

within

the

S. Sa-

, R.

Schwenn,

Vilhu

will,

SUMER

to-

Science

the scientific requirements and recommend their to the SUMER team. The Associate Scientists

will participate

in the

Acknowledgements: knowledge uical

SUMER

The

the support

Team,

hardt,

in

operation

and

SUMER

the

the

investigators

of the Associate

particular,

H. Hartwig,

in preparing

1. Athay

H.-J. SUMER

R G 1985,

current 100, 2.

data

analysis.

of C. Meyer,

Becker,

and the Tech-

P.

Boutry,

J. Osantowski,

and

proposal

on which

like to ac-

would

Scientists

this

W.

Engel-

R. Schmidt

report

is based.

status

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