NASA Technical Reports Server (NTRS) 19930020567: Mars Aquarius Mission and Titan Explorer

The Mars Aquarius Mission is designed to carry out several scientific studies of the surface and subsurface of Mars with an emphasis on locating subte...

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N93-29756 305

MARS

AQUARIUS

MISSION

AND

TITAN

EXPLORER

U. S. NAVAL ACADEMY

MARS AQUARIUS

pointing antenna, each used Both antennas are mounted

MISSION

for both transmitting and receiving. on the despun section of the space-

Philosophy

craft. The groundbased component of the communications will involve the use ofa 70-m dish, part of NASNs Deep Space Network

The Mars Aquarius Mission is designed to carry out several scientific studies of the surface and subsurface of Mars with

(DSN). A 500-kin

an emphasis

orbit provides

for low path loss for the uplink,

the necessary

overhead

on

a precursor

locating

subterranean

to a manned

mission

water.

This

mission

to Mars. A manned

is

mission

orbit

will require an extended stay on the planet's surface, and an accessible source of water will greatly simplify life support

reception

requirements.

predetermined

Using data from previous

sites have been selected

as possible

The Aquarius sites.

carries

spacecraft

Mars observations,

locations

four

of subsurface

one penetrator

water.

for each

of these

hundred

and injected landing

and

fifty-five

days

will be simultaneously on hyperbolic

sites.

Upon

and a parachute

after

trajectories

atmospheric

launch,

released

toward

entry,

that will decelerate

all four

requires

their

each

the penetrator

time of three orbiter

spacecraft

will

store

four

kbits.

of the

landing

the penetrator The

will be blasted

penetrators

periments.

site,

carry

The

at impact

major near

ray spectrometer and

minor

the surface

will determine

elements,

housing

of

out

control

power

system

chosen

for the Aquarius

This

system

met

panels. power

ex-

as well

of water throughout and atmosphere. The the abundance

required,

the

and safety.

as a few

of Mars. Temperature

probes

trace

Maximum

generator,

a 2-W

provide

visual

microradioisotope

as well as lithium

batteries

is relayed up to the orbiter via a half-wave a 0.5-W transmitter at a maximum rate A diagram

data

of the penetrator

thermo-

L

Transmitter/ Receivar

Forebod?

Earth-pointing

umbilie

Electronics

ea

for power.

.....

is shown

p .....

]i

Data

(ORS)

in Fig. 1.

.-s /./

x-r.y/--

i_/

The Mars Aquarius communications system must be able to receive commands from Earth, transmit signals to the penetrators to initiate their transmission of data, receive and store this data, Basic components

needed

Accelcrometer_

dipole antenna and of 11.1 kbytes/s at

Communications

and telemeter

power

q

carries

both

this data

and status

of the communications dish

and

a half-wave

array

of vehicle

array

Im_gor

the

will

a 360 ° camem/imager

on landing sites. Each penetrator

take

elements,

will measure

activity.

220 MH_

is a solar

requirements

of most

Accelerometers and a of the planet and seismic

electric

will

_ubsystem

_--

reports system

turnstile

back

to Earth.

include

a 3-m

reflector

Mars-

Descent

a

a day. This

!touatng MeLOorotogy

Solar

several

planet's temperature-depth profile. seismometer will analyze the structure Also,

times

Downlink

and alpha-backscatter/

XRF spectrometer will detect the presence the surface, subsurface, permafrost layers, gamma

until

is designed

shield

into the soil.

to carry

spectrometer

orbit

into a ballistic

lower

4-6 m further

instruments

neutron

the

for data

at 19 kbps and 8.4 GHz.

approach. Landing accuracy is approximately 5 km. Impact will occur at velocities from 80-100 m/s. Depending on the composition

This

of data from

it in memory

via DSN. The

of 31.9

needed

reception

can uplink

storage

orbiter.

and also provides

minutes

Upon

and thermal

weight,

respective

has a heat

The

for the

penetrators.

penetrator

maximum

of eight

from the spacecraft

the

chosen

time to downlink

so that any given

Power

penetrators

the

penetrators,

30 minutes

Penetrators Two

the

from

was

tmager

Fig. I. Aquarius Penetrator.

306

Proceedings

onboard

the

spacecraft

is 340 W. Each

each panel alone is capable Since

the spacecraft

wrapped

around

maximum

incidence.

will

be times

41.03

min.

eclipse.

during

however, solar

in series,

which

Advanced

Design

Program

m 2, and

the panels

cells

7th

Commond

Summer

a_ld

data

Conference

storage

times

are

axe always

orbit of the orbiter,

Maximum

these

NASA/USRA

eclipse

time will

will be provided

will be reconditioned

in

there be

by 22

after each

of use in eclipse.

Thermal

constraints

by the batteries.

craft.

against

temperature

Multithermal

section, tanks,

active

the

cold

periods

when

system

rise too high.

Figures

space.

are employed

blankets

heat

used

aluminum

shield

over

Active systems

no sunlight

for heat

10 ° to

Both

active

on the spaceon

the

despun

on the propellant the 490-N include

can provide

dissipation

2 and 3 show

determined

allows the sun to evenly

of outer

regulation

steel

entirely

be kept within

otherwise

the passix_e portion.

louver

must

on the antennas,

and a stainless

for eclipse

are nearly

cells

insulation

black paint

comprise

NiCd

spacecraft

the orbiter

and passive

onboard

The

25 ° C. The spinning heat

stabilized, enough

is 5.747

the

the 340-W requirement.

Due to the polar

of solar

NiCd batteries period

is spin it so that

Power

panel

of producing

of

should

engine

two heaters heat,

and an

temperatures

top and side views

Aquarius spacecraft and include elements of the tions, propulsion, power, and thermal systems.

of the

communica490N

thr_,zter

Fig 3. Aquarius Spacecraft, Side View. Astrodynamlcs

and aerobraktng

To conserve spacecraft is utilized. The spacecraft

weight, a minimum energy transfer will begin the Mars transfer from

an Earth will

booms

The

stowed

orbit the

change

entire

of 300

on a Hohmann

also place

a plane Antenna

parking

the spacecraft

spacecraft

transfer

will

take

enter

22N

will

the

orbit with orbit.

to-drag

of

from Antenna

booms

ratio

Black

Three

is

quarters

a AV of 0.459

of m/s,

the

for the spacecraft.

atmosphere

of 4.159

The

at a flight

km/s.

The

path

aerobraking

spacecraft

by 0.6323

km/s,

a periapsis

of 100 km and an apoapsis

a AV of 27.6 m/s will place

The

aerobrake

is a blunt

1:2. It is composed

tiles and

calculated

deployed

martian

a velocity

slow

in a circular of ceramic

thrusters

days.

will impart

requirements

the

of -20 ° with

maneuver

/

This

fuel

reduces will

of 500 km. At apoapsis _i

plane.

28.5 ° inclination.

This greatly

in an elliptical

tracKercKe/'/r

258.96

engine

ecliptic orbit's

on a path that will result in a polar martian will be accomplished using aerobraking.

angle

Star

AV will place

placing the spacecraft orbit. Mars capture spacecraft

Penetrators

in Mars'

of 6.5 ° from the parking

the way to Mars, the 490-N

r

kin. A 3.696-km/s

transfer to Mars. The thrust vector

unfolds

shuttle

bay.

as April

26, 2001.

after

The

resulting

the spacecraft

body

with

a lift-

of an isogeometric the

optimum

spacecraft

grid

is removed

launch

date

has

for the

transfer

been

palnt

Propulsion The

propulsion

spacecraft

_:[Lna j

the

system

must

provide

of the

fyom Earth orbit to Mars, and for stationkeeping

martian

Aquarius

orbit

is attained.

spacecraft

km Earth orbit,

with

The space its transfer

positioning

shuttle kick

it in the proper

once

will deploy

motor

into

attitude

the

a 300-

for transfer.

At this time the aerobrake will be deployed and the 3-m Earth communications dish extended. The 3.696-km/s AV is provided

Graphite Epoxy

BlanKets

E:_G

Earth 22N

thrusters

Antenna

by the

Orbus

booster

that

three-axis Fig. 2. Aquarius Spacecraft, Top View.

21 will

Transfer carry

stabilization.

be perpendicular

Orbit

5347 During

Stage

(TOS),

kg of propellant.

a solid The

transit the spacecraft's

to the Sun, allowing

the solar panels

rocket

TOS uses y axis will to achieve

U. S. Naval

307

Academy

maximum

incidence.

Three-axis

stabilization

will

star trackers

onboard

be used

at

a nuclear

thermal

rocket,

of the

velocity

purpose. Attitude control is provided by a bipropellant system of one 490-N engine and twelve 22-N thrusters. Upon achieving

studies

have proposed

Mars orbit,

reactor

this time.

The spacecraft

has four

the despin

will be spun

hub will be unlocked

up to 25 rpm. Star trackers

for this

bed

and the spacecraft

on the despun

reactor

made

will

could

be

necessary such

developed for this

a system

up of uranium

be used

2400-3000

section

changes

to heat

that would

and carbon

hydrogen

use a particle

alloy pellets.

The

an exhaust

of

nozzle.

a specific

impulse

proposed

a rocket

of service,

of 1134 kg and would deliver over 34,000 kg of thrust. This rocket would require 10,580 kg of fuel to complete the proposed

after

planetary can then missions.

which

time

the

Titan

Explorer

of an orbiter

be placed

in

trajectory.

EXPLORER

is a scientific

and a lander

circular

orbit around

of Titan's

Titan

atmospheric

of magnetic

fields,

research

designed

moon, Titan, to conduct various and send data back to Earth.

sphere, The around

will

places TITAN

The

spacecraft

quarantine for probable future resta__. The spacecraft be used again as a communications relay for future

probe

to travel

experiments, The probe

make observations, will be placed in a

and will make preliminary

composition observations

and structure,

estimates

measurements

of the dynamics

of Titan's

atmo-

and radar observations of the topography of Titan. lander will be deployed by the probe after the orbit Titan has been established. It will attempt to measure

the composition

and variations

land

a solid

on

either

conditions

or

and composition

The Titan its main

Explorer

propulsion

dish makes

without shuttle

system

as it descends,

and

determine

the

in shape

along

surface.

is 10 m long and octagonal

the top of the spacecraft by NASKs space

surface,

of Titan's

axis. A high-gain

of the spacecraft

of the atmosphere

liquid

antenna,

folded

its height

fuel is 2743 it on

on

2.4 m. The total mass kg. It will

in the year 2015

to send

and stored

be launched

and will use a nuclear

a six-year

journey

to Titan.

to power system, motors.

for the

orbiter

is the

General

specific

power

systems,

surface composition Saturn's distance

and conditions. from Earth and the Sun makes

Titan

problem.

a significant

using a gravity assist into a 300-km-aititude change

of 3.8 km/s

the ecliptic.

Another

approximately

on

Titan

Explorer

will

and

to Saturn

energy

decay

at various primarily

for

use

from

the

heat

of radioisotope

the scientific

given

off

fuel. The RTGs

instruments,

command

and

communications systems, heaters, pumps, The total estimated power requirement

is 390

W. The

Purpose (54.4

amount

which

Heat

Wc/kg)

most

recently

Source

make it a good

of power

required

developed

RTG

(GPHS)-RTG.

Its

candidate

high

to provide

by this mission.

580 W at the beginning of the mission. After to Titan, their total output will have decayed Attitude

determination

sensors

and

star

stabilization

provide

while

three-axis

six hydrazine

and control

trackers

system

wheels

with

the

The Titan

momentum

corrections

Titan's

data

to

wheels.

with

some

to

by Sun

a three-axis

The

momentum

will

Explorer's

gather

atmospheric

transit

gyroscopic

and adjustments

The Titan

instruments

the six-year to 475 W.

will be performed

supplying

spacecraft

thrusters.

concerning

stiffness

be made

orbiter

preliminary

by

carries

six

information

composition

and

dynamics,

topography, and magnetic fieM. A solid-state imaging will be used to determine atmospheric structure,

motions,

just reaching get

located

Explorer will use two such RTGs that will be deployed on extendable booms after launch. They have the capacity to provide

surface camera

weather

radioactive

data handling and electric

the large

(RTG)

electrical

will be used

emissions,

atmosphere,

also

will be used

thermoelectric

generators

to produce

scientific

field,

are

these

have a mass

by radioisotope

Upon reaching Titan, it will use at least 15 different scientific instruments to accomplish its objectives of studying Titan's magnetic

but

have

thermoelectric by the natural

largest

thrusters

spacecraft,

estimates

m that would

maintaining and altering its orientation. Power for the main spacecraft will be provided couples

consisting

to Saturn's

m × 1.22

Six hydrazine

on the

s, preliminary

With

will provide stationkeeping dat_ The Aquarius spacecraft has sufficient fuel onboard for a minimum of two martian years

3.05

1000

all

Recent

gas to temperatures

K and then eject it through of roughly

to provide

trajectory.

and radiative

motions.

properties

and will study

A photo-polarimeter-radiometer

relative

will

cloud

measure

the

flyby of Jupiter. It will first be launched Earth orbit by the shuttle. A velocity

temperatures and energy as cloud characteristics

will

spectrometer the clouds.

will use spectra to study the atmosphere above The orbiter also carries a gamma-ray spectrometer

which

attempt

be

AV burn a Hohmann

used

to move

of 6.3 km/s transfer

it to the

plane

of

will put the spacecraft orbit

to Jupiter,

which

will

balance of the atmosphere, as well and composition. An ultraviolet

to investigate

will take approximately 2.7 years. It will fly past Jupiter at a distance of 206,700 kin, gaining about 10.0 km/s from this flyby.

elements by measuring gamma-ray radar altimeter will be used to

It will

mapping

travel for another

2.8 years

and

then

use a 5.87 km/s

of the

surface

the composition

of surface

emission characteristics. provide some topogt_hic

in an effort

to determine

the

amount

burn to reach a parking orbit with a radius of 1.3 million km around Saturn. It will then use a Hohmann transfer around Saturn

of liquid and solid surface and possibly adjust the entry trajectory of the lander. A magnetometer, extended from the spacecraft

to get to its circular surface. The launch

by a boom, will measure any magnetic Titan. These six instruments require

orbit around Titan, 2000 window for this trajectory

constrained

by the angular

and Saturn. in 2015.

The

In order better by

launch

between window

the Sun, Jupiter, would

open

late

power. Communications through

to use this trajectory,

than those

to carry

relationship

first practical

km above its is primarily

extremely

the proposed

available large launch

a propulsion

system

today will be needed amounts in 2015,

significantly

to avoid having

of fuel.

It was

such

a system,

assumed

that

specifically

receiving a rate

with

rates of

of up

15 GHz

communications diameter

the

DSN. It is assumed

parabolic

to

field that exists around approximately 77 W of

spacecraft

will

that DSN's

current

12 GHz

will

be

mission

launch

system

onboard

the spacecraft

high-gain

antenna

be

conducted

transmission/

improved

by dish

A

time. that

to allow

The

primary

uses

a 5.8-m-

will

require

308

Proceedings

l18W

of power

and will

broadcast

at a frequency

of 15 GHz

of

the

with

NASA/USRA

altitude

of the

to meet the required data transfer of 135 kbps. A secondary system will consist of two parabolic dish low-gain antennas.

atmosphere

They are each

flux radiometer

1.35 m in diameter

and will operate

of 14.9 GHz and 14.8 GHz. During the

high-gain

spacecraft when

antenna

and covered

the probe

used. When systems

the probe's folded

Titan,

shroud.

the lander is deployed,

land

dipole

antennas

in a conical

relay

of the

antennas

a solid

or

attached

front of the spacecraft.

to communicate

has been

entry into Titan's

atmosphere,

a liquid

and

surface,

float

if

on a flat, 1.3-m platform base. The is surrounded with a vacuum-filled to the orbiter,

the

aeroshell

It will be deployed

established

the

the lander

will

be deployed,

turn,

releases

been

deployed,

the

lander

module's

Once

lander

lander

is encased around

tennas.

out

of the path

orientation, which

the the

the atmosphere,

pull

heat

drift slowly

adjust

a pilot

chute

off the aft cover

which,

Once

chute

parachute.

conical

orbiter,

and start it on its entry trajectory.

will

main

of the

shield

to Titan's

the

main

will

be jettisoned

surface,

studying

in

the

size

estimated power Kapton blankets lander

systems

excess

heat

and

Kapton

the

lander

surface

the descent The

and a double

from

the

multilayer from

(estimated

The lander

of a normal

GPHS-RTG.

output of 136 W after will be used to insulate

the

closed

RTG to an atmospheric blankets extremely

to be about

atmospheric

and others structure

radiator.

Mylar

to insulate

cold

temperatures

of Tim's

instruments

to be used

experiment

will

during

on the surface.

study

know

two The

omnidirectional, orbiter

when

lander's

the variation

samples to locate

main

and

clouds.

characte_tics

The

will

will

quarter

lander

will

it is within

sight

and

goals

of the

Titan

establish

data

carry

able

orbit

moon.

many

To complete

should

to receive

mission

are

to reach enter

and survive some

and

Tim's

to send

questions

such a mission, technological such advances

data. The

up to 3 Gbits

Titan,

of the basic

an-

rate of 50 kbps.

can store

around

be able to successfully

via the dipole

to let the lander

data transfer

Explorer

an

had to be made concerning by the year 2015. Provided Explorer

system

and data handling system equals 9.5 orbits of data.

successfully

be conducted

wavelength,

use a beacon

system will have a maximum

The command of data, which The

(C,H,N,S,O,P). with the orbiter

back

about

this

assumptions

advances achievable can be made, Titan

perform

its mission.

A£:KNO_JEDGMENTS

an

also be used

to

of the

collected samples. A micro gas chromatograph the distribution and molecular forms of the

planet-like

transfer

be used

structure,

in the

determines

and

will

to be used while

system

to answer

atmo-

will

of cloud

and morphology.

safely land on its surface,

94 K).

will carry scientific phase

will

navigation

A net

of Titan's

also analyze

particles

enough

It will provide

system

of the

cloud

layers.

will be carried

measurements

of the

components

and will

atmosphere,

six years. Multilayer the RTG from other

loop

altitudes

major

has

spheric composition and conditions as it descends. Power for the lander will be provided by a scaled-down version of the GPHS-RTG. This smaller version will be a little more than half

and

topogt-aphy

biogenic elements Communications

once

have

spectrometer

of the

of Titan. A nephelometer

used to analyze will determine

lander's

observations

understanding

ma_

character

density

levels, internal

a better

A neutral

make direct

and

of cloud

Conference

a cryogenic xenon sample collector and an alpha-particle instrument and an in.situ chemical analysis instrument will be

on the

the orbit

pressure,

Summer

of cloud

abundances

the

camera

and is carried

and preliminary

unit has entered

will

layers,

7th

and altitudes

provide

at different

of the surface

The

been made by the orbiter's scientific instruments. Four hydrazine thrusters mounted in the atmospheric entry shell will be used the lander

the

determine

It is made up of a 1-m-diameter

atmospheric-entry

to maneuver

budget.

determine

cloud

the lander

will

radiation atmosphere

will be

communications

between

will be used

is encountered.

spherical housing mounted bottom half of the lander While

to Titan,

top

Until it is deployed

the orbiter

to survive

either

the latter situation

shroud.

the

Program

temperature,

and the depths

of surface

is designed on

journey

along

the secondary

will act as a communications

The lander

Titan

be

by a protective

reaches

and Earth. Two with the lander. safely

will

Design

as well as conditions

structure,

at frequencies

Advanced

Mars Aquarius

Mission

smmnm T prepared

Dulla, Christina Glaser, Jason Lopez, Jef_eyLucas, and James

by Ensigns Michelle

Brian Reyes,

Rimrodt.

Tital Explorer Paul Diedrich,

summary

prepared

by Ensigns

Stephen

Terry Ladau, David Laga._a, and John

Philpott,

Soma.

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