Outline Scientific Background Payload Mission Profile - - PDF document

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Study of Active Mainbelt Object through Sample Acquisition

Summer School Alpbach 2008 BLUE TEAM

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Outline

• Scientific Background
• Payload
• Mission Profile
• Planetary Protection
• Budgets
• Critical Issues
• Conclusions

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Introduction

• What is SAMOSA?

– Sample return mission to a main belt comet (MBC) – Return a sample of ~50g – In-situ investigation and remote sensing

• Why?

– MBC are unusual objects and not well understood – They may give us information about:

• Stellar evolution
• Planet formation
• Emergence of life
• Why a sample return?

– Equipment on earth is more precise – More answers could be found – More questions will emerge

• - In 2006, a population of objects was discovered in the
• Main Belt showing cometary activity
• Main-Belt Comets (MBC)
• - Currently three such objects are known:
• 133P/ Elst-Pizarro

176P/ LINEAR

• P/2005 U1 Read

What are Main-Belt Comets (1)?

• For EP the activity is definitely driven by sub-

limation of volatiles on the surface:

• Finson-Probstein modelling confirms continuous activity
• ver at least 5 months along the orbit
• Activity was observed at the same orbital position in 3

consecutive apparitions (1996, 2002, 2008), inactivity at

• ther parts

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• Water is not stable at the surface in the Main Belt over

long periods

It must have been stored below the surface for some 109 a An impact must have exposed it to sunlight recently The crater surface is young (<103 a?) There is no regolith in the crater area

What are Main-Belt Comets (2)?

The Themis Family

What are Main-Belt Comets (3)?

The MBCs are members of the Themis Family of asteroids:

• Dynamically it fits
• They have the BVRI colours of C-type asteroids, but not of comet nuclei

and TNOs

• It is dynamically unlikely to insert a comet

to an orbit in the Main Belt

• There are indications that water ice is present on the surface of 24 Themis
• Orbits in the Themis Family are long-term stable

The MBC are former members of a now disrupted protoplanet still containing volatiles They are still close to their formation region in the pre-solar disk

The Themis Family

• Some asteroids are clustered in families with similar orbital

elements and similar spectroscopic properties

What is the Themis Family?

• These families were formed by the collisional disruption of a larger parent

body (protoplanet)

• The Themis Family is one largest families:
• primitive C-type asteroids
• largest object (24 Themis) ~200 km in diameter
• parent body was ~380 km in diameter
• parent body was disrupted ~ 2 Ga ago

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What to do?

What to do at the MBC?

• Aquire a sample of volatile and non-volatile material from one MBC go in the crater
• Get a sample that includes sub-surface material (>1cm) drilling
• Determine the morphological and mineralogic context on the MBC global mapping
• Return some tens of grams of the sample to Earth re-entry
• Determine the physical microstructure in situ microscopic investigation

What to do on the way to the laboratory?

• Keep the sample below 0°C at all times avoid aqueous alteration
• Monitor the temperature continuously trace the sample environment
• Ensure high level of cleaness to minimize contermination with terrestrial material

avoid analysis of terrestrial organics

• Ensure high density of the sample container avoid loss of volatiles in space

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What to do?

What to do at the MBC?

• Aquire a sample of volatile and non-volatile material from one MBC go in the crater
• Get a sample that includes sub-surface material (>1cm) drilling
• Determine the morphological and mineralogic context on the MBC global mapping
• Return some tens of grams of the sample to Earth re-entry
• Determine the physical microstructure in situ microscopic investigation

What to do on the way to the laboratory?

• Keep the sample below 0°C at all times avoid aqueous alteration
• Monitor the temperature continuously trace the sample environment
• Ensure high level of cleaness to minimize contermination with terrestrial material

avoid analysis of terrestrial organics

• Ensure high density of the sample container avoid loss of volatiles in space

...AND WHY?

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Link to pre-planetary disk

Modelling Results for the pre-planetary disk:

Si in minerals as a function of distance from the proto-Sun Concentration of hydrocarbons as a function

• f distance to the proto-Sun
• Models of the pre-planetary disk provide

the abundance of materials as a function

• f the distance from the proto-Sun
• The comparison with observations allows us to

constrain the conditions in the pre-planetary disk

• The model results depend on a number of

parameters (turbulence, initial mass, diffusion,...) A sample from a MBC (volatiles and non-volatiles, well

constrained formation region) allows to constrain the

conditions in the pre-planetary disk

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Temperature versus time in a 20 km-size body.

• Orbits in the Themis Family are stable over

long times (order Ga): Formation distance from proto-Sun well constrained

• Themis Family is well known

Size and nature of the protoplanet parent body is constrained

• Crystallisation age determination is possible

The time of formation can be determined

• Minerals and volatiles allow us to constrain the

temperature regime Maximum temperature/pressure in history can be determined

• The cooling rate can be determined

The burial depth during formation can be constrained

No other object provides such a large number

• f well-constrained parameters!

Link to Planet Formation

Modelling Results for Planet Formation:

Correlation between distance from Sun, accretion time, protoplanet diameter, and temperature.

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Link to Meteorites

• Carbonaceous chondrites are the oldest meteorites

available on Earth

• They contain organic matter
• They are partly affected by aqueous alteration
• The alteration products (carbonates) are important for isotopic studies
• C-type asteroids (Themis Family) are the assumed parent

bodies of the carbonaceous chondrites A sample from a MBC provides the first link between the meteorite collections on Earth and astronomical objects It is possible to correlate isotopic and elemental composition of different minerals and volatiles (water) in the parent body

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• Impact studies suffer from poor constraints on basic

material properties (internal energy, equation of state,...)

• Such properties can be constrained from the conditions during an impact
• The Themis Family was disrupted in an catastropic collision and volatiles

are present in fragments The volatile compostion can constrain the maximum temperature in the body during impact The understanding of the conditions during impacts is important for the history of Earth: What material (water, organics) delivered to Early Earth survives the impact? What is available for the formation of life?

Link to Impact Science

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Link to the Origin of Life

• Most water on Earth does not come from comets:

D/H in SMOW : 15.6 x 10-5 D/H in water in the cometary coma is twice that value

• Does the water come from the Main Belt?
• What is D/H in other organic compunds?
• Carbonaceous Chondrites contain organic material
• Their parent bodies have impacted on the Early Earth

What organic material was present on the Early Earth? Isotopic analysis in the volatile sample can determine the origin of terrestrial water The laboratory analysis allows to make an inventory of organic matter that came to Earth in Impacts

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Sample Analysis

Why return a sample?

Planet Formation Dating Isotopic composition Planet Formation Cooling rate Elemental composition on microscale Origins of Life Organic composition high precision & sensitivity Planet Formation, Protoplanetary disk Microscopic mineral composition high spatial resolution Origins of Life Isotopic ratios in minor volatile species high accuracy and sensitivity

This implies:

The required analysis needs:

• Ground-bound instrumentation (TEM, SIMS, GC-MS,...)
• Sample decisions
• Complex sample preparation
• Analysis adaptivity

The Sample has to be returned to ground

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Overview: Analysis of the returned sample

Imaging

Sample microstructure Optical Microscopy, SEM Sample topography AFM Elemental distribution SEM-EDX, TEM-EELS Cooling rate SEM-EDX, TEM

Bulk and Mineral Composition

Bulk elemental composition ICP-AAS, X-Ray Tomography 3D elemental distribution ToF-SIMS, nano-SIMS Mineral structure TEM, RAMAN, X-ray Diffraction

Volatiles and Organic Compounds

Identification of soluble and volatile compounds GC-MS, HPLC-MS, MALDI Identification of non volatile and non soluble compounds Cluster Ion ToF-SIMS Structure investigations NMR techniques, MS-MS

Isotopic investigations (e.g. Age Dating)

Crystallization age High resolution MS (ICP-MS, nanoSIMS, solid state MS, Laser ablation MS…) Radiation age H/D ration (ice)

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What Ground-Based Support?

• The selection of the most suitable target requires further characterisation of the

MBC

• We know:

Object Radius [km] Period ∆v [km/s] Colours

Elst-Pizarro 3.0 x 2.1 3.5 h 8.8 BVRI LINEAR 2.2 n.a. 8.9 n.a. Read 1.1 n.a. 9.3 n.a.

• We need:
• better sizes photometry
• better shapes photometric light curves
• rotation periods photometric light curves
• classification low resolution spectrometry
• times of activity imaging, Finson-Probstein
• quantification of the dust activity photometric imaging
• quantification of the gas production spectrophotometry
• BVRI imaging can be done with medium to large telescopes
• Spectral information can be obtained with large telescopes
• CN as a tracer of gas activity can be studied with large telescopes

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Payload Requirements

What to do at the MBC?

• Aquire a sample of volatile and non-volatile material from one MBC
• Get a sample that includes sub-surface material (>1cm)

Drilling – Core Extraction Device

(Lander)

• Determine the morphological and mineralogic context on the MBC

Optical Cameras (HR, WA, stereo)

(Orbiter)

Laser Altimeter + Radio Science

(Orbiter)

Visible-Near-IR spectrometer

(Orbiter)

Mid-IR spectrometer

(Oribter)

Alpha Partice X-ray Spectrometer

(Lander)

• Return some tens of grams of the sample to Earth

Re-entry capsule

• Determine the physical microstructure in situ

Microscopic Imager

(Lander)

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High Resolution Camera (HRC) Mass: 1.2 kg Dimension: 15x10x10 cm Detector: APS (2k x 2k) Wavelength range: 400 – 900 nm FoV: 1.47 deg Power:2.5 W Data rate: 100kbit/s uncompressed Thermal constrains:

• 40 – 30 °C

High Resolution, Wide Angle cameras Stereo Imaging

The cameras are used to provide the necessary information about the morphology and topography of the target. They will be used to:

• map the entire surface
• get stereo images of the target in combination with the laser altimeter

data

• choose the landing site

Wide Angle Camera (WAC) Mass: 0.3 kg Dimension: 5x5x7 cm Detector: APS (2k x 2k) Wavelength range: 400 – 700 nm FoV: 40x40 deg Power:3 W Data rate: 100kbit/s uncompressed Thermal constrains:

• 40 – 30 °C

Payload and Scientific Instrumentation

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Laser Altimeter

Provides the necessary information about the distance of the MSC to the surface

• f the target. In combination with the stereo image, the derivation of a 3D model

is possible.

Laser Altimeter Mass: 3.3 kg Dimension: 14x12x12 cm Detector: APD diode Wavelength range: 1064 nm FoV: <20 arcsec Power: 15 W Data rate: 150kbit/orbit compressed Thermal constrains: 10 – 40°C operation

• 30 – 60°C preservation

Payload and Scientific Instrumentation

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Mid-Infrared Spectrometer

• Remote investigation of the thermophysical properties of the target
• Chemical and mineralogical information of the surface of the target will

be obtained

Mid-IR Spectrometer Mass: 2.5 kg Dimension: 15x15x10 cm Detector: uncooled Micro- bolometer Wavelength range: 8-16 µm FoV: 4.0 deg Power:5 W Data rate: 3.6 Mbit/image Thermal constrains:

• 40 – 30°C

Payload and Scientific Instrumentation

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Visible Near Infrared Spectrometer

• Remote sensing of the surface of the target to gain information about

mineralogical and chemical composition

• Observation of overtone vibrations and electronic excitations

Vis-Near-Infrared Spectrometer Mass: 2.3 kg Dimension: 15x10x5 cm Detector: MCT Wavelength range: 0.4 – 1 µm 1 - 3 µm FoV: 0.25 mrad Power: 8 W Data rate: Close mapping 300 Mbit Thermal constrains:

• 50°C

Payload and Scientific Instrumentation

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Radio Science Antenna: Ø1.5m HGA Wavelength range: Ka-band (32GHz) X-band (8GHz)

Payload and Scientific Instrumentation

Radio Science (radio subsystem of the MSC)

• Information about the mass of the body
• Estimate the gravity field

Doppler shift of two downlink radio carrier frequencies (X-band and Ka- band) of the radio subsystem of the MSC, as well as the data of the Laser altimeter and the stereo image, will be applied for that reason

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Microscope Imager

• Characterize the morphological conditions of the sampling site
• Bore hole images

(In order to lower the device into the hole and investigate sideward the instrument has to be modified so that the camera has a flexible pointing direction)

Microscope Imager Mass: 0.7 kg Dimension: 10x10x7 cm Ø < 1 cm periscope Detector: APS (2k x2k) Wavelength range: 400-700 nm FoV: 31.5 x 31.5 mm Power: 3 W Data rate: ~50 Mbit/image Thermal constrains:

• 40 – 30°C

Payload and Scientific Instrumentation

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Mission Profile

II Gravity assist to Mars

MBC Earth

I Gravity assist to Earth 26

Transfer to Target

Outbound leg

Launcher AR5 ECB (Kourou) Launch Arrival date Transfer time 09 March 2020 15 October 2025 2056 days ( ~5.7y)

• main transfer with SEP
• 2 Gravity assist: Earth & Mars
• Final target arrival burn with chemical

propulsion system Transfer Parameter ∆v Launcher ∆v SEP ∆v Chem Propulsion 2236.0 m/s 5311.3 m/s 1656.6 m/s

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Approach and Sampling

Approach

• Orbit of 1 km around the target for remote sensing measurements
• Selection of suitable landing site
• Deployment of lander at an altitude of 500 m
• Descent time: ~ 40 min
• AOCS with monopropellant hydrazine

Sampling

• Anchoring lander by harpoons to prevent rebound during sampling
• Storage of max. 150g sample in container
• Deployment of container with a spring loaded separation device
• Orbiter will capture canister at altitude 50m
• Storage of canister in re-entry capsule
• Landers remains on surface for in-situ measurements

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Return Transfer to Earth

Return leg

Launch target Arrival date Transfer time 01 April 2026 02 June 2030 1523 days (~4.2y) Transfer Parameter ∆v SEP 3360.6 m/s

• Time of stay: 6 months
• Use of SEP for transfer
• Additional revolution at Earth to lower

entry velocity (12.6 km/s)

• Deployment of ECR, collision

avoidance maneuver

• Entry with 12.6 km/s at FPA 13°

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Spacecraft

6.1 m 5.1 m 4.31 m 1.7 m 1.7 m lander

• rbiter

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Orbiter

electric propulsion chemical propulsion antenna re-entry vehicle payload

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Propulsion system of Orbiter

Electrical propulsion ∆v = 8.7 km/s Total Thrust = 400 mN 2 HET thruster PPS500 : 200 mN

4 PPU, 2 High Pressure Flow Control 4 Low pressure Flow Control, 4 Tanks Harness

4 thruster for redundancy

Chemical propulsion Bipropellant (also for the AOCS maneuvers) ∆v = 1.66 km/s Main engine for the ∆v maneuvers EADS 400N Thrust 420±20 N Nominal Mixture ratio 1.65 Mass 3.6 kg Nominal Isp 318s

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Power system of Orbiter

1.1 kW Power supplied (3.4 AU) 44 m2 Panel area 198 kg Panel mass 12.5 kW Power supplied (1 AU) 18 kg Battery Mass 16 Cells number 180 Wh Cell capacity 2.8 kWh Total capacity required

Triple junction GaAs solar cells Deployable and sun-pointing Li-ion cells (20%DoD) Charge control required Discharge control requirements depend on bus architecture Due to high power levels separated power regulation for SEP is required

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AOCS of Orbiter

Spacecraft is 3-axis stabilized

• Inertial sensors
• Star trackers
• Solar sensors
• Navigation camera to find the

target

• LASER altimeter
• Advanced Video Guidance

Sensor (AVGS) to track sample canister during its ascent from the lander

• 4 reaction wheels

(3 + 1 spare)

• 24 chemical orientation

thrusters (6 degrees of freedom + redundancy) for angular momentum dumping and hovering

• ver the lander

Bradford engineering

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Thermal system of Orbiter

• Remarkable

differences in thermal conditions: almost factor of 16

• Highly flexible thermal

system required

• System keeps

temperature in range from 0°C to 20°C

• Multiple Layer Insulation (MLI)

surface

• radiators:

– engine cooling (variable- conductance heat pipes) – spacecraft cooling (regulated by louvers)

• insulation and cooling of

particular instruments

• thermal sensors
• electrical heaters

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Communication system

• Ø1.5m HGA
• 35 W
• 40 kbps (≤5 AU)
• Ka-band
• Ø0.25m LGA
• 1 W
• 200 kbps (≤25 km)
• UHF-band
• ESA ESTRACK
• 35m HGA
• Ka-band

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Data Handling

• Challenge:
• Guidance Navigation & Control (GNC) and science instruments

produce high amount of data (sev. Mbps), which has to be processed quickly

• Fast data transfer between instruments, buffer, memory and

transmitter required

• Solution:

– LEON III Processor (sev. Hundred MIPS, easy scalable, low power) – SpaceWire network (10 Mbit/s -> 200 Mbit/s, easy scalable) – Storage Memory as additional buffer

Lander uses similar but less complex configuration

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Lander

payload anchor drill canister antenna rotating table

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Lander

• The Lander, named Ginger, contains the necessary

equipment for in-situ and sub-surface measurements, as well as the anchorage system

• It is equipped with four legs, each designed with a

deformable honeycomb structure to dissipate most of the impact energy

• The legs provide additional anchorage due to

penetration of the surface upon firing the thrusters

• The Lander also utilises two anchoring harpoons, to

withstand forces due to the drill

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Power system of Lander

12 m2 Panel area 54 kg Panel mass 134 W Total power supplied (60°) 130 W Total power required 2.2 kg Battery Mass 2 Cells number 180 Wh Cell capacity 308 Wh Total capacity required

Triple junction GaAs solar cells Deployable (60° sun angle considered) Li-ion cells (55%DoD) Charge control required

• Two operational modes: “landing” and “surface”
• The landing mode is supposed completely supplied by batteries
• In the “on surface mode” the batteries supply power to the sampling

mechanism (pulse load like) Possibility to perform one drilling attempt immediately after the landing

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AOCS of Lander

Attitude stabilization

• Inertial sensors
• 24 chemical orientation

thrusters (6 degrees of freedom) Landing on the target

• RADAR altimeter
• Navigation for Planetary

Approach and Landing system (NPAL)

• Thrusters (landing

position)

EADS Astrium

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Thermal system of Lander

• designed to be able to operated during the

day and to survive night on the MBC

• thermal stability achieved by:

– Multiple Layer Insulation (MLI) – electrical heaters

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Sampling

• The Lander system will perform a sub-surface sampling

with the drill which is located on the lower surface of a rotating table

• The rotating table is 700mm diameter and designed to

allow movement in the vertical and rotational directions

• The sample system contains a drill, a stationary tube

(fixed to the turn table), a corer and a closing mechanism

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Sampling and Storage

• The rotation shaft

and transfer tube are fixed on the stationary platform

• The rotating table

enabling optimal sampling site to be located upon arrival

Return canister

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Drilling mechanism

• The stationary tube

connected to the rotating table contains the corer, which fills with sample as the drill rotates

• When the corer is filled, it

is pushed away from the stationary tube

• As it moves up the

closings seals are deployed

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Corer sealing mechanism

• The sealed corer is

transferred through the stationary tube to the sample container

• The drill is then retracted

and the turn table rotated to position under transfer tube

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Sample transfer mechanism

• The corer is secured in

the sample container and the table is rotated to apply the explosive seal

• The sample container is

then transferred into the passive cooling mechanism through the sample transfer tube via a reel mechanism

• The return canister is

rotated and sealed and ready for deployment to the return capsule

Return canister

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Sample Canister

Sample Sample container Volatile absorber Support / damper Lid Water/Ice jacket Explosive seal

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Catching the Sample Canister

• The orbiter is

hovering over the lander (h ~ 50 m)

• Canister is

launched vertically from the lander using springs

• Tracking of the

canister by Advanced Video Guidance Sensor

• Orbiter catches the

canister

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Re-entry capsule

• Mass estimate: 54 kg
• Entry speed:12.6 km/s
• No parachute but high energy

absorption material to reduce g- loads

• Landing ellipse diameter ~20 km
• Quick recovery and transport to

curation facility

• Beacon for localization

Picture from study overview of the near earth asteroid sample return

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Planetary Protection

• Outbound leg and Orbit-Phase:

Only remote chance to contaminate the target. → COSPAR Category II

• Sampling and Return Phase:

→ COSPAR Category V

• Comets (and C-Asteroids) belong the “unrestricted Earth return”

Subgroup of Catergory V. i.e. no special Containment and Handling warranted except for scientific purpose.

• Science: All devices in direct contact with cometary material must be

cleaned to a level below detection limits. i.e. drill, core, sample containment and the legs of the lander

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Orbiter Mass Budget (Total) System Mass [kg] incl. Margin Lander Module wet mass 249.1 Return Modul wet mass 2293.8 Total Orbit dry mass (launch) 2542.9 Propellant (SEP) 714.5 Propellant (Chem.) 1793.7 Total wet mass 5051.1 Return Module Mass Budget Subsystem Mass [kg] Mass incl. 20% Margin [kg] AOCS 65.49 78.59 OBDH 19.0 22.8

• Comm. (UHF)

58.4 70.08 Payloads 12.36 14.83 Power System 246.0 295.2 Thermal 87.6 105.1 Propulsion (SEP) 227.0 272.4 Propulsion (Chem.) 422.2 506.7 Structure 282.0 338.4 Mechanism 31.9 38.3 Harness 56.4 67.7 Return Capsule 54.2 65.1 Total dry mass 1562.6 1875.2 Propellant (SEP) 316.8 Propellant (Chem.) 101.8 Total wet mass 2293.8 Lander Mass Budget Subsystem Mass [kg] Mass incl. 20% Margin [kg] AOCS 21.89 26.27 OBDH 3.0 3.6

• Comm. (UHF)

5.0 6.0 Payloads 2.16 2.59 Sampling System 16.2 19.44 Power System 82.5 99.0 Thermal 8.0 9.6 Structure 37.2 44.64 Mechanism 13.92 16.7 Harness 12.72 15.26 Total dry mass 202.59 243 Propellant (Hydrazine)* 6 Total wet mass 249.1

Mass budget

* The hydrazine is used in the lander AOCS system

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Lander Power Budget Subs. power in light (W) power in night (W) AOCS* (68) (68) OBDH 5 5 Comm 5 5 Payloads 7 7 Sampling Mech.** (100) (100) Thermal 20 EPS Power required 17 37 Margin (%) 20 20 Total 20.4 44.4

Power budget

*The power required by AOCS and sampling mechanism are provided by the batteries and considered as pulse loads ** The sampling mechanism is considered a pulse like load and supplied by the batteries Orbiter Power budget Subs. Power (W) Electrical Propulsion 10000 AOCS 129 OBDH 10 Comm. 70 Payloads 35.3 Sampling mech. 10 EPS 5 Thermal 100 Power without margin 10359.3 Margin (%) 20 Total 12431.16

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Cost budget

• Launcher

190 M€

• Ground segment & Operations

100 M€

• Space segment

1900M€

• Total

2190M€

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Critical Issues

• Ground Based Observation Campaign needed during the all mission process
• Payload and Sampling system inherited from existing or under development

missions with TRLs ranging from 4 to 9 (Marco-Polo, Exomars, Hayabusa, Bepi Colombo, Planet C, MERs)

• The research and development needed will be done during Phase B and C.

List of critical issues for our mission: Availability of AR5 ECB Launcher Vision based guidance system for landing Sampling system Sample ejection and capture system

2009 2010 2014 2018 2020 2030 Phase A Phase B Phase C Phase D Operation Preliminary analysis Preliminary Definition Detailed definition Production and Support Design Ground Based Observation Campaign Ground Qualifcation Testing

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Conclusions

• SAMOSA will provide answers to several

fundamental questions about the solar system history

• It is a challenging mission, first studies

show that the mission is feasible with current technologies

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Credits

We thank Oliver and Peter, and the roving tutors for excellent support, and Johannes Ortner and his team for an intensly exiting time!

Felix Bexkens Ludivine Boche-Sauvan Guillaume Boubin Carlo Del Vecchino Blanco Mathias Hemberg Mark McCrum Norah Patten Bernhard Schiffer Bernhard Schlappi Christian Schmid Christoph Straif Aurora Ullan Michael Weiler Jana Weise

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• Backup Slides?

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Re-entry capsule

kg 54.228 Total dry with marign kg 9.038 % 20 System margin kg 45.19 38.1 Total dry. 1.06 0.48 0.08 20 0.4 Harness 1.46 0.66 0.06 10 0.6 Power 2.55 1.155 0.055 5 1.1 Communication 12.6 5.695 0.695 13.9 5 Mechanisms 45 20.4 3.4 20 17 Thermal Control 37 16.8 2.8 20 14 Structue % kg kg % kg Fraction Total Margin Input Margin Input Mass

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Re-entry capsule

• Entry velocity 12.6 km/s
• γentry 13°
• Maximal deceleration ~55g
• Landing impact < 1000 g
• Maximal heat load ~200 MJ/m2
• Maximal heat flux ~12.5 MW/m2
• Arrival velocity ~40 m/s
• Maximal dynamic pressure ~4atm
• PICA material → heat loads imply an ablative

TPS thickness ~50 mm

• High energy absorption material → RVC

Picture from study overview of the near earth asteroid sample return