asteroseismology: looking inside stars

Asteroseismology: Looking inside stars

Jørgen Christensen-Dalsgaard & Hans Kjeldsen Aarhus Universitet

Rømer

Asteroseismology:Looking inside stars

5

Mission Objective and Critical mission requirements

Rømer (1999-200?)

Rømer Payload: MONS Telescope DesignOrbitPlatform Design

10

Mission Objective and Critical mission requirements

Rømer primary mission objective

To provide new insights into the structure and evolution of stars, using them as laboratories tounderstand physics under extreme conditions, by studying oscillations in a sample of 20 solar-typestars.

Mission Objective and Critical mission requirements

Rømer secondary mission objectives

1. To study the structure and evolution of stars hotter and more massive than the Sun (delta Scuti and rapidly oscillating Ap stars) by measuring their oscillations.

2. To study variability in a large sample of stars of all types.

Mission Objective and Critical mission requirements

Scientific aims (Rømer):

• Properties of convective cores, including overshoot• Structure and age of low-metallicity stars• Physical properties of stellar matter• Stellar helium abundances• Effects and evolution of stellar internal rotation• Dependence of the excitation of oscillations• Surface features• Convective motions on stellar surfaces• Reflected lights from exoplanets (and transits)

Mission Objective and Critical mission requirements

Rømer Payload Objectives

• Photometric precision: We must be able to detect oscillations that have very low amplitudes (1-10 ppm)

• Temporal coverage: Each primary target must be observed almost continuously for at least one month, ideally substantially longer

• Sky coverage: The science goals require access to the whole sky over the course of the mission

Colour oscillation signal

Solar data from VIRGO on SOHO

Key mission parametersMission parameter Description

Size 60 x 60 x 71 cm

Primary payload MONS optical telescope and Field Monitor

Secundary instruments 2 star imagers

Weight 99 kg

Power consumption 55 Watt, average

Downlink datarates Max. 24 Mbyte/day

OrbitHighly elliptical (Molniya)

Apogee: 40.000 km - Perigee: 600 kmInclination: 63.4

Launch SOYUZ/FREGAT

32 cm telescope

Field Monitor

Star Tra

cker #

1

Star Tra

cker #

2

15

Image on CCD

Molniya orbit: Rømer

Orbit is a 400 x 40,000km 63.4° inclination

a = 26600 km i = 63.4 e=0.75 P=11.967 hrs.

Change in right ascension of theascending node:

-0.030 deg/day

Change in argument of perigee:

0.000 deg/day

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

20

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude Determinationand Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude DeterminationAnd Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command andData HandlingSubsystem

ADCS:Attitude DeterminationAnd Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command andData HandlingSubsystem

ADCS:Attitude DeterminationAnd Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command and DataHandling Subsystem

ADCS:Attitude DeterminationAnd Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command andData HandlingSubsystem

ADCS:Attitude DeterminationAnd Control Subsystem

Communication

Structure andMechanisms

PowerThermal

CDH:Command andData HandlingSubsystem

Ground-based support observations

Preparatory observations•Characterization of targets (effective temperature, luminosity, composition)

•Charcterization of target field, including possible interfering objects

Parallel observations•For some objects, simultaneous ground-based velocity observations, for characterization of strongest modes.