• Occulting the Star.umbras.org/publications/poster/aiaa_poster_35x60_6i.pdfthis away from the...

1
Major Functional Components: Sun Shade Occulting Screen Pedestal/Cassette & Boom • Bus Solar Arrays Propulsion Modules & Boom UMBRAS: Design of a Free-Flying Occulter for Space Telescopes Ian J. E. Jordan, Helen Hart, Alfred B. Schultz; Computer Sciences Corporation Fred Bruhweiler; Catholic University of America Dorothy Fraquelli, Forrest Hamilton, Mark Kochte; Computer Sciences Corporation Abstract: A free-flying occulter used with a space-based telescope can enhance the contrast in the region close to a star, allowing extrasolar planet searches. An occulting spacecraft design, emphasizing configuration, control, propul- sion, mass estimates, and power requirements, is presented requiring no extension of existing technology or exotic engineering solutions. The design is scalable for use with telescopes having 1 to 10 metre apertures. Several inno- vations are employed to block starlight and suppress scattered sunlight. A station keeping control method is possi- ble using various thruster types. Solar electric propulsion enables scientifically useful observation rates and allows the occulting craft to be packaged on existing launchers with no on-orbit assembly. Design Launch Packaging Control Operations Sun Shade Scalability UMBRAS (Umbral Missions Blocking Radiating Astronomical Sources) is a class of missions as well as a technique. The general design is scalable for small as well as large occulters. Below is a representative set of missions classes and their general mission design characteristics. Mission Telescope Screen Mission Class Aperture Size Duration E-Class (Explorer) ~ 1 m ~5-8 m ~1+ years D-Class (Discovery) 1-4 m 10-30 m 2+ years N-Class (NGST) 4-10+ m ~45 m up to 6 years Functionally, the occulting screen is used for two purposes: Occulting the Star. Hiding other spacecraft structures (e.g., bus, solar array) from the telescope. MLI screen construction emphasizes: optimizing science thermal characteristics for N-class infrared missions. preserving science utility by mitigating meteoroid impact damage The Sun Shade allows minimal scattering of sunlight toward the telescope since it shades the entire side of the screen facing the telescope. At left we see a cross-section for packaging a large N-class occulter into a Titan-IV fairing or Shuttle payload bay. The solar arrays fold flat against the bus. The propulsion booms fold longitudinally, and the cassette housing the occulting screen is pulled in next to the bus. The Sun Shade is also folded to fit within the fairing. At left is a diagram of an N-class occulter bus with the propulsion booms folded to place the modules alongside the spacecraft bus. Folding rigid booms allow the num- ber of flexible propellant line connections to be minimized. Placement of Attitude & Translation Control (ATCS) thrusters on the bus is shown, with nozzle size exagger- ated for clarity. UMBRAS/SPIDER Features: Occulting Screen unfurled from ‘window shade’ cassette on Screen Pedestal. Controlled 1-time unfurling of Screen & Propulsion Boom Deployment ‘Curtain track’ to create larger screen from overlapping layers. Bistems or coiled Astromasts for shade/screen support. Sun Shade shields screen from direct solar exposure during observations. Screen/Pedestal articulates for: * transit to provide symmetry for thrust control. * observations to hide bus/array/propulsion from telescope. Propulsion Module on boom(s) minimizes contamination & interference. Xenon propellant tanks stored in bus. Solar Electric Propulsion offers significant observation rates. Attitude/Translation Control thrusters mounted on Bus & Propulsion Module. 3-axis stabilization for stationkeeping, maneuvering, & transits. Above is a control block diagram showing a scheme for controlling the rel- ative position of the occulter with respect to the telescope. Imaging of the occulter against the background stars by cameras onboard the telescope allows the occulter to be appropriately positioned. Shown above is the general scheme of coplanar force-couples, with the center of mass in the plane of the couple, enabling attitude and trans- lational control amidst science observations. Thruster plume impingement on the screen is avoided. Attitude control thrusters are located on the propulsion module (B) and the spacecraft bus (A) and allow some T-axis translational motion with little impact on the observation. The occulter would appear bright to a telescope if it were not shaded from the sun (a problem for most previous free-flying occulter ideas). The plot at left shows the equivalent brightness (in astronomical magnitudes) of a sphere with the same pro- jected area as a 45-metre N-class occulter at various distances (log of separation in metres). An unshaded structure, is quite bright. At left is a close-up of the spacecraft along with its reflection off of the occulting screen. Bistem or astromast supports for the screen- and-shade (shade not within field of view) are visible both directly and in reflection rising from the cassette-pedestal structure. Occulter and telescope must operate far from Earth to minimize the effects of differential gravitation on stationkeeping. At right (not to scale), the sun, telescope, and occulter lie in a plane. The occulter is positioned such that the telescope is in the star-shadow cast by the occulter. The occulter spacecraft bus is hidden from the telescope by the screen. The transit configuration allows simpler control of the spacecraft. The diagrams above and below show the observing and transit configurations of UMBRAS’ occulter for two different mission classes. AIAA 2000-5230 Plan views above are of the observing configura- tion shown from three different perspectives: “Above” occulter, looking from the sun. From the telescope. From the “side” The artist’s rendition above shows the occulter viewed from the target-star side of the screen in its observing configuration. The underside of the bus and solar arrays are visible in the foreground in front of the screen. Astromasts or bistems are shown connecting and sup- porting the top and bottom of the screen. Characteristic Solar Array and Bus Sizes for SPIDER in various mission classes. Mission Solar Array Solar Array Solar Array Bus Class Y-width +X-wing -X-wing E-class 4 m 4 x 0.8 m 4 x 0.4 m 1.2 x 1.2 x 1.2 m D-class 4 m 6 x 1.0 m 4 x 0.5 m 1.5 x 1.5 x 4 m N-class 12 m 5 x 1.0 m 4 x 0.4 m 1.5 x 1.5 x 6-8 m At left, the N-class occulter transits with the sun in the plane of the occulting screen to minimize solar heating of the screen. This helps the screen reach a lower tem- perature, enabling utility at longer wavelengths than if the screen had to dissipate heat absorbed by more direct solar exposure during transits. Below, the E- and D-class occulters do not need the extra twist placing the sun in the plane of the screen that the N-class do since smaller telescopes are not likely to be efficient planet hunters at wavelengths where thermal emission by the screen would compromise science objectives. 3-D renderings of an N-class UMBRAS Occulter courtesy of Edward Rowles, Multi- Image Productions, http://starships.com/Multi-Image/MIP_Home.HTML At right, is a view from the sunward side of the bus/array. SPIDER is configured for observing. SPIDER operation requires articulating the occulting screen into a symmetric configuration for movement between targets. At left is a conceptual dia- gram showing snapshots of an N- class occulter’s configuration at dif- ferent times as viewed from above the telescope- occulter-target plane. Phases (A) and (I) represent successive stations on different Target-Telescope Lines-of-Sight (different science targets). The phases in between show snapshots of the occulter at representative moments during the journey between targets. Articulate the screen into transit position. Orient occulter toward next Target-Telescope Line-of-Sight. Acceleration toward next Target-Telescope Line-of-Sight. Mid-course turnover Deccelerate to a halt. Alignment of Occulter along Target-Telescope Line-of-Sight. Articulate screen into observing configuration. Distinct phases of target-to-target transit operations: CORVET is a proposed demonstration mission that could validate the external free-flying occulter technique. http://www.stsci.edu/~jordan/umbras/ At left is the same diagram as described above, however the propulsion booms have been deployed. Note that the propul- sion modules have swung into their opera- tional place. The number of required booms depends upon the number of engines and the packing factor within the launch fairing. Here, we assume 24 required engines. However, fewer may be needed for smaller missions, or for NSTAR engines with longer life carbon- carbon cathodes replacing current molyb- denum ones. Placement of ATCS thrust- ers on the propulsion module is also shown. UMBRAS employs a sun shade to shield the screen from sunlight. The Shade’s razor-like edge is designed to mini- mize sunlight scattering from the edge into the telescope. At right is shown the bright- ness of diffuse and specular edges illuminated by the sun, for two different edge sharp- nesses. Note that the edge is much less bright than the spheres shown above. The specular curves are for an ori- entation with the brightness at a maximum (viewer perpen- dicular to the edge). Properly oriented, the shade reflects most of this away from the telescope. Vapor deposition of a micro-bead- ing material on the edge could strike a balance minimizing over- all light scattered into the telescope. Best guess upper limits on the mass and power budgets for 3 different sized UMBRAS Occulter mission classes. Coronagraph & Occulting Rover, V isible Exoplanet T elescope Single launch (both craft) onboard Atlas II AS Near-Earth Solar-orbit or L2 ~ 1-metre space telescope (~1000 kg) o Unoccluded, off-axis primary mirror o Focal plane coronagraphic imager Occulter (<1300 kg) w/ o 5- to 8-metre occulting screen o 1 NSTAR XIPS engine o Fuel for 1-2 year mission o 50 bright targets, 2 visits each o Jovian search 0.25” - 4” at λ = 0.5 µ SPIDER = Solar- Powered Ion- Driven Eclipse Rover Solar Electric Propulsion for primary propulsion is sufficient to achieve science goals. NASA/Hughes NSTAR engines are baselined for this mission. XIPS or cold-gas thrusters may be used for the ATCS (Attitude & Translation Control Sub- Mass & P o wer Estimates f or UMBRAS Missions E-class D-class N-class 5-metre Screen 10-metre Screen 45-metre Screen Mass/Po wer/Dimensions: Mass/Po wer/Dimensions: Mass/Po wer/Dimensions: Payload: extensible screen 13 kg 52 kg 360 kg shade 10 kg 20 kg 60 kg screen cassette 20 kg 40 kg 90 kg bus-screen boom 30 kg 30 kg 70 kg metrology (beacons) 10 kg [50 W] 10 kg [50 W] 30 kg [50 W] (inc booms) pedestal & masts 50 kg 100 kg 130 kg P ayload subtotal: 123 kg 252 kg 710 kg Bus + Array: Structure: array support 12 kg 20 kg 50 kg bus + propulsion boom 75 kg 100 kg 200 kg Power Production & Storage: Arrays (GaAs @ 18% BOL) 168 kg {4.2 kW} 280 kg {7kW} 600 kg {15 kW} Power Control & Conversion 175 kg 300 kg 680 kg Battery : (450 W-hrs NiH2 ) 10 kg 10 kg 10 kg Propulsion: NSTAR @92mN (η m =.85) 17 kg (1) 102 kg (2 op. of 6) 408 kg (6 op. of 24) Power Conditioning/Control 30 kg [~0.3 kW] (1 units) 120 kg [~0.6 kW] (4 units) 300 kg [~1.5 kW] (10 units) Xe propellant storage tanks ~ 30 kg ~ 130 kg ~1200 kg Xe pressure & feed system 50 kg [100 W] 50 kg [100 W] 50 kg [100 W] Attitude & position determination & control: ACS (16 UK-10 @25mN) - < 120 kg (4 x 0.7 kW) < 120 kg (4 x 0.7 kW) ACS aux (16 N2 @5N + pinholes) 40 kg [100 W] 40 kg [100 W] 40 kg [100 W] N2 tanks + feed system + 25 kg N2 100 kg 100 kg 100 kg sun sensors (4 units) 4 kg [12W] 4 kg [12W] 4 kg [12 W] star trackers/optical navigation cameras 3 kg [40 W] (2 unit) 6 kg [80 W] (4 units) 6 kg [80 W] (4 units) gyros & reaction wheels 26 kg [150 W] (4 each) 42 kg [150 W] (6 each) 142 kg [500 W] (6 each) Communications: Communications (low gain), 2 units 50 kg [70 W] 50 kg [70 W] 150 kg [170 W] Command, Control & Data I/O: 50 kg [50 W] 50 kg [50 W] 50 kg [50 W] Thermal Contr ol: --- 10 kg 20 kg 30 kg Bus + Array subtotal 853 kg 1527 kg 4223 kg Dry mass: 986 kg 1779 kg 4933 kg Mar gin ~ 20% (total dry mass): 197 kg 356 kg 987 kg Xenon Propellant 100 kg 440 kg 4000 kg T otal mass (inc. propellant) : < 1278 kg < 2700 kg < 9860 kg Different sized missions use different sized launchers. The E- or D-class occulters may be launched from Atlas II AS sized boosters or smaller. The largest conceived N-class occulter might need a shuttle, Titan IV-class vehicle.

Transcript of • Occulting the Star.umbras.org/publications/poster/aiaa_poster_35x60_6i.pdfthis away from the...

Page 1: • Occulting the Star.umbras.org/publications/poster/aiaa_poster_35x60_6i.pdfthis away from the telescope. Vapor deposition of a micro-bead-ing material on the edge could strike a

Major F

unctional Com

ponents:

•Sun Shade

•O

cculting Screen•

Pedestal/Cassette &

Boom

•B

us•

Solar Arrays

•Propulsion M

odules & B

oom UM

BR

AS: D

esign of a Free-F

lying Occulter for Space Telescopes

Ian J. E. Jordan, H

elen Hart, A

lfred B. Schultz; C

omputer Sciences C

orporationFred B

ruhweiler; C

atholic University of A

merica

Dorothy Fraquelli, Forrest H

amilton, M

ark Kochte; C

omputer Sciences C

orporation

Abstract:

A free-flying occulter used w

ith a space-based telescope can enhance the contrast in the region close to a star,

allowing extrasolar planet searches. A

n occulting spacecraft design, emphasizing configuration, control, propul-

sion,mass

estimates,and

power

requirements,is

presentedrequiring

noextension

ofexistingtechnology

orexotic

engineering solutions. The design is scalable for use w

ith telescopes having 1 to 10 metre apertures. Several inno-

vationsare

employed

toblock

starlightandsuppress

scatteredsunlight.A

stationkeeping

controlmethod

ispossi-

bleusing

variousthruster

types.Solarelectric

propulsionenables

scientificallyusefulobservation

ratesand

allows

the occulting craft to be packaged on existing launchers with no on-orbit assem

bly.

Design

Launch Packaging

Control

Operations

Sun ShadeScalability

UM

BR

AS (U

mbral M

issions Blocking R

adiating Astronom

ical Sources) is a class of missions as

well as a technique. T

he general design is scalable for small as w

ell as large occulters. Below

is arepresentative set of m

issions classes and their general mission design characteristics.

Mission

TelescopeScreen

Mission

Class

Aperture

SizeD

uration

E-C

lass (Explorer)

~ 1 m~5-8 m

~1+ years

D-C

lass (Discovery)

1-4 m10-30 m

2+ years

N-C

lass (NG

ST)

4-10+ m

~45 mup to 6 years

Functionally, the occulting screen is used for tw

o purposes:

•O

cculting the Star.•

Hiding other spacecraft structures (e.g., bus, solar array) from

the telescope.

ML

I screen construction emphasizes:

•optim

izing science thermal characteristics for N

-class infrared missions.

•preserving science utility by m

itigating meteoroid im

pact damage

The Sun Shade allow

s minim

al scattering of sunlight toward the telescope since

it shades the entire side of the screen facing the telescope.

At left w

e see a cross-section forpackaging a large N

-class occulterinto a T

itan-IV fairing or Shuttle

payload bay. The solar arrays fold

flat against the bus. The propulsion

booms fold longitudinally, and the

cassette housing the occultingscreen is pulled in next to the bus.T

he Sun Shade is also folded to fitw

ithin the fairing.

At left is a diagram

of an N-class occulter

bus with the propulsion boom

s folded toplace

them

odulesalongside

thespacecraft

bus. Folding rigid booms allow

the num-

ber of flexible propellant line connectionsto

bem

inimized.

Placementof

Attitude

&T

ranslation Control (A

TC

S) thrusters onthe

busis

shown,w

ithnozzle

sizeexagger-

ated for clarity.U

MB

RA

S/SPID

ER

Features:

•O

cculting Screen unfurled from ‘w

indow shade’ cassette on Screen Pedestal.

•C

ontrolled 1-time unfurling of Screen &

Propulsion Boom

Deploym

ent•

‘Curtain track’ to create larger screen from

overlapping layers.•

Bistem

s or coiled Astrom

asts for shade/screen support.•

Sun Shade shields screen from direct solar exposure during observations.

•Screen/Pedestal articulates for:

* transit to provide symm

etry for thrust control.* observations to hide bus/array/propulsion from

telescope.•

Propulsion Module on boom

(s) minim

izes contamination &

interference.•

Xenon propellant tanks stored in bus.

•Solar E

lectric Propulsion offers significant observation rates.•

Attitude/T

ranslation Control thrusters m

ounted on Bus &

Propulsion Module.

•3-axis stabilization for stationkeeping, m

aneuvering, & transits.

Above

isa

controlblockdiagram

showing

aschem

efor

controllingthe

rel-ative position of the occulter w

ith respect to the telescope. Imaging of the

occulter against the background stars by cameras onboard the telescope

allows the occulter to be appropriately positioned.

Shown above is the general schem

e of coplanarforce-couples, w

ith the center of mass in the

plane of the couple, enabling attitude and trans-lational control am

idst science observations.T

hruster plume im

pingement on the screen is

avoided. Attitude control thrusters are located

onthe

propulsionm

odule(B

)and

thespacecraft

bus (A) and allow

some T-axis translational

motion w

ith little impact on the observation.

The occulter w

ould appearbrightto

atelescope

ifitwere

not shaded from the sun (a

problem for m

ost previousfree-flying occulter ideas).T

he plot at left shows the

equivalent brightness (inastronom

ical magnitudes) of

a sphere with the sam

e pro-jected area as a 45-m

etre N-class occulter at various distances

(log of separation in metres). A

n unshaded structure, is quitebright.

At left is a close-up of

the spacecraft alongw

ith its reflection off ofthe occulting screen.B

istem or astrom

astsupports for the screen-and-shade (shade notw

ithinfield

ofview)are

visibleboth

directlyand

inreflection

risingfrom

the cassette-pedestalstructure.

Occulterand

telescopem

ustoperatefarfrom

Earth to m

inimize the effects of differential

gravitation on stationkeeping. At right (not

toscale),the

sun,telescope,andocculter

liein a plane. T

he occulter is positioned suchthat the telescope is in the star-shadow

castby the occulter. T

he occulter spacecraft busis hidden from

the telescope by the screen.

The

transitconfigurationallow

ssim

plercontrolofthespacecraft.

The

diagrams

aboveand below

show the observing and transit configurations of U

MB

RA

S’ occulter fortw

o different mission classes.

AIA

A 2000-5230

Planview

sabove

areof

theobserving

configura-tion show

n from three different perspectives:

•“A

bove” occulter, looking from the sun.

•From

the telescope.•

From the “side”

The artist’s rendition above show

s the occulter viewed

from the target-star side of the screen in its observing

configuration. The underside of the bus and solar arrays

are visible in the foreground in front of the screen.A

stromasts or bistem

s are shown connecting and sup-

porting the top and bottom of the screen.

Characteristic Solar A

rray and Bus Sizes for SP

IDE

R in various m

ission classes.

Mission

Solar Array

Solar Array

Solar Array

Bus

Class

Y-w

idth+X

-wing

-X-w

ing

E-class

4 m4 x 0.8 m

4 x 0.4 m1.2 x 1.2 x 1.2 m

D-class

4 m6 x 1.0 m

4 x 0.5 m1.5 x 1.5 x 4 m

N-class

12 m5 x 1.0 m

4 x 0.4 m1.5 x 1.5 x 6-8 m

Atleft,the

N-class

occultertransits

with

thesun

inthe

planeof

theocculting

screento

minim

izesolar

heatingof the screen. T

his helps the screen reach a lower tem

-perature, enabling utility at longer w

avelengths than ifthe screen had to dissipate heat absorbed by m

oredirect solar exposure during transits.

Below

, the E- and D

-class occulters do not needthe extra tw

ist placing the sun in the plane of thescreen

thattheN

-classdo

sincesm

allertelescopesare not likely to be efficient planet hunters atw

avelengths where therm

al emission by the

screen would com

promise science objectives.

3-D renderings of an N

-class UM

BR

AS

Occulter courtesy of E

dward R

owles, M

ulti-Im

age Productions,http://starships.com

/Multi-Im

age/MIP_H

ome.H

TM

L

At right, is a view

from the sunw

ard side of thebus/array. SPID

ER

is configured for observing.

SPIDE

R operation

requiresarticulatingthe

occultingscreen

into a symm

etricconfiguration form

ovement betw

eentargets. A

t left is aconceptual dia-gram

showing

snapshots of an N-

class occulter’sconfiguration at dif-ferent tim

es asview

ed from above

the telescope-occulter-target plane. Phases (A

) and (I) represent successive stations on differentTarget-Telescope

Lines-of-Sight

(differentsciencetargets).

The

phasesin

between

show snapshots of the occulter at representative m

oments during the journey

between targets.

•A

rticulate the screen into transit position.•

Orient occulter tow

ard next Target-Telescope Line-of-Sight.

•A

cceleration toward next Target-Telescope L

ine-of-Sight.•

Mid-course turnover

•D

eccelerate to a halt.•

Alignm

ent of Occulter along Target-Telescope L

ine-of-Sight.•

Articulate screen into observing configuration.

Distinctphasesof

target-to-targettransitoperations:

CO

RV

ET

is a proposed demonstration m

ission that couldvalidate the external free-flying occulter technique.

http

://ww

w.stsci.ed

u/~

jord

an

/um

bra

s/

At left is the sam

e diagram as described

above, however the propulsion boom

shave

beendeployed.

Note

thatthepropul-

sionm

oduleshave

swung

intotheir

opera-tional place. T

he number of required

booms depends upon the num

ber ofengines and the packing factor w

ithin thelaunch fairing. H

ere, we assum

e 24required

engines.H

owever,few

ermay

beneeded for sm

aller missions, or for

NSTA

R engines w

ith longer life carbon-carbon cathodes replacing current m

olyb-denum

ones. Placement of A

TC

S thrust-ers on the propulsion m

odule is alsoshow

n.

UM

BR

AS em

ploys a sun shade to shield the screen fromsunlight. T

he Shade’s razor-like edge is designed to mini-

mize

sunlightscatteringfrom

theedge

intothe

telescope.

At right is show

n the bright-ness of diffuse and specularedges illum

inated by the sun,for tw

o different edge sharp-nesses. N

ote that the edge ism

uch less bright than thespheres show

n above. The

specular curves are for an ori-entation w

ith the brightness ata m

aximum

(viewer perpen-

diculartothe

edge).Properly

oriented,theshade

reflectsm

ostofthis

away

fromthe

telescope.V

apordeposition

ofa

micro-bead-

ing material on the edge could strike a balance m

inimizing over-

all light scattered into the telescope.

Best guess upper lim

its on the mass and pow

er budgets for 3 different sized UM

BR

AS O

cculter mission classes.

Coronagraph &

Occulting

Rover,

Visible

Exoplanet

Telescope

•Single launch (both craft) onboard A

tlas II AS

•N

ear-Earth Solar-orbit or L

2

•~ 1-m

etre space telescope (~1000 kg)o U

noccluded, off-axis primary m

irroro Focal plane coronagraphic im

ager

•O

cculter (<1300 kg) w

/o 5- to 8-m

etre occulting screeno 1 N

STAR

XIPS engine

o Fuel for 1-2 year mission

o 50 bright targets, 2 visits eacho Jovian search 0.25” - 4” atλ =

0.5µ

SPIDE

R =

Solar-

Pow

ered

Ion-D

riven

Eclipse

Rover

SolarElectric

Propulsionforprim

arypropulsion

issufficientto

achieve science goals. NA

SA/H

ughes NSTA

R engines are

baselined for this mission. X

IPS or cold-gas thrusters may be

used for the AT

CS (A

ttitude & T

ranslation Control Sub-

Mass &

Pow

er Estim

ates for UM

BR

AS M

issions

E-class

D-class

N-class

5-metre Screen

10-metre Screen

45-metre Screen

Mass/Pow

er/Dim

ensions:M

ass/Power/D

imensions:

Mass/Pow

er/Dim

ensions:P

ayload:extensible screen

13kg

52 kg360

kgshade

10 kg20 kg

60 kgscreen cassette

20 kg40 kg

90 kgbus-screen boom

30 kg30 kg

70 kgm

etrology (beacons)10 kg

[50 W]

10 kg[50 W

]30

kg[50 W

] (inc booms)

pedestal & m

asts50 kg

100 kg130 kg

Payload subtotal:123

kg252 kg

710kg

Bus +

Array:

Structure:array support

12 kg20

kg50 kg

bus + propulsion boom

75 kg100

kg200 kg

Power P

roduction & Storage:

Arrays (G

aAs @

18% B

OL

)168

kg{4.2 kW

}280

kg{7kW

}600

kg{15 kW

}Pow

er Control &

Conversion

175 kg300 kg

680 kgB

attery : (450 W-hrs N

iH2 )

10kg

10kg

10 kg

Propulsion:

NSTA

R @

92mN

(ηm

=.85)

17kg

(1)102 kg

(2 op. of 6)408 kg

(6 op. of 24)

Power C

onditioning/Control

30kg

[~0.3 kW] (1 units)

120kg

[~0.6 kW] (4 units)

300 kg[~1.5 kW

] (10 units)X

e propellant storage tanks~

30kg

~130

kg~1200 kg

Xe pressure &

feed system50

kg[100 W

]50

kg[100 W

]50 kg

[100 W]

Attitude &

position determination &

control:A

CS (16 U

K-10 @

25mN

)-

<120

kg(4 x 0.7 kW

)<

120 kg(4 x 0.7 kW

)A

CS aux (16 N

2 @5N

+ pinholes)

40kg

[100 W]

40kg

[100 W]

40 kg[100 W

]N

2 tanks + feed system

+ 25 kg N

2100

kg100 kg

100 kgsun sensors (4 units)

4kg

[12W]

4kg

[12W]

4 kg[12 W

]star trackers/optical navigation cam

eras3

kg[40 W

] (2 unit)6

kg[80 W

] (4 units)6 kg

[80 W] (4 units)

gyros & reaction w

heels26

kg[150 W

] (4 each)42

kg[150 W

] (6 each)142 kg

[500 W] (6 each)

Com

munications:

Com

munications (low

gain), 2 units50

kg[70 W

]50

kg[70 W

]150 kg

[170 W]

Com

mand, C

ontrol & D

ata I/O:

50kg

[50 W]

50kg

[50 W]

50 kg[50 W

]

Therm

al Control:---

10 kg20 kg

30 kg

Bus +

Array subtotal

853 kg1527 kg

4223 kg

Dry m

ass:986 kg

1779kg

4933 kg

Margin ~ 20%

(total dry mass):

197 kg356 kg

987 kg

Xenon Propellant

100kg

440 kg4000 kg

Total mass

(inc. propellant):< 1278 kg

< 2700 kg< 9860 kg

Differentsized

missions

usedifferentsized

launchers.T

heE

- or D-class occulters m

ay be launched from A

tlas II AS

sized boosters or smaller. T

he largest conceived N-class

occulter might need a shuttle, T

itan IV-class vehicle.