Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA (ITALIAN SPRING ACCELEROMETER):
AN ACCELEROMETER TO MEASURE THE INERTIAL ACCELERATIONS
ACTING ON THE MPO.
Iafolla V. and the ISA Team
[email protected]
V. Iafolla
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26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA team
•IFSI (Istituto di Fisica dello Spazio Interplanetario), INAF, Rome Italy
• AAS_I
•Harvard-Smithsonian Center for Astrophysics Cambridge MA, USA
•Sternberg Astronomical Institute, University of Moscow Russia
•Space Research Centre, Warsaw Poland
Task
PI
Electrical Engineer
Steering Committee Member
Steering Committee Member
Tracking Co-I
Gravitational effects evaluation.
Error budget evaluations Co-I
Theoretical analysis Co-I
Electrical Engineer Responsible
System Engineering Manager
Thermo-Mechanical Responsible
PA Manager
EGSE Responsible
Instrument Project Manager
SW Responsible
MGSE
V. Iafolla
Name
Valerio Iafolla
Sergio Nozzoli
David Lucchesi
Giancarlo Bellucci
Luciano Iess
Vadim Milyukov
Enrico Lorenzini
Janusz B. Zielinski
Luca Boschini
Luca Soli
Francesco Colombo
Marina Cesareo
Marco Concolino
Maurizio Balasini
Vania Vettorello
Roberto Pavesi
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Acceleration acting on ISA installed on a satellite
The acceleration on a point P (ISA proof–mass) close to the MPO COM is:
  
        
R    g R      R    R  2   R  ANGP




Acceleration due to the
planet gravity field gradients


Angular acceleration
Non–Gravitational
accelerations
Coriolis acceleration
Z
Centrifugal acceleration

Inside the MPO
frame
X
V. Iafolla

ISA proof–mass

R
Y

g = Planet gravity;
 = MPO angular rate:

 = MPO angular acceleration;

 = MPO–proof–mass vector;
R
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Key rôle of ISA accelerometer
The main NGP acting on the MPO in Mercury’s thermal environment are:
• Direct solar radiation pressure;
• Mercury albedo (indirect radiation pressure);
• Mercury infrared radiation;
The more important in terms of the magnitude of the disturbing acceleration
on the MPO orbit are:
1.
the solar radiation acceleration:
 1106 m s 2
2.
Mercury albedo acceleration:
 3 108 m s 2
V. Iafolla
1ST MORE TEAM MEETING
26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Key rôle of ISA accelerometer
Mercury’s albedo radiation pressure
An order of magnitude estimate:
AMer  RMer  A  Sun AMer  RMer 
1
a Alb 

aSun



 aSun 
2  a  m c
2  a 
32
2
2
ĀMer  0.12
represents the average Bond albedo
RMer  2439 Km
represents Mercury’s equatorial radius
a  3389 km
represents the MPO semi–major axis
In a simplified approach the albedo acceleration has a component along
both the radial and solar direction.
V. Iafolla
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26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Reference Frame
The GAUSS co-moving frame:
R

radial component;
T

transversal component;
W

out-of-plane component;
ŵ

ˆ
A  Rrˆ  Ttˆ  Ww
tˆ
rˆ  tˆ  wˆ
r̂
V. Iafolla
1ST MORE TEAM MEETING
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Solar Radiation: Radial acceleration
3 orbital periods  7 hours
1 Orbital period
Radial acceleration (m/s 2)
1,0x10-6
½ Orbital period
1/3 Orbital period
5,0x10-7
0,0
-5,0x10-7
-1,0x10-6
-1,5x10-6
100
0
5000
10000
15000
20000
108 m/s2
25000
Time (seconds)
The perturbing effect at the
orbital period (2.3 h) is about
2 orders–of–magnitude
larger than the
accelerometer accuracy of
 108 m/s2
V. Iafolla
No modelling of the solar radiation
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Solar Radiation: Transversal acceleration
1,5x10-6
3 orbital periods  7 hours
Transversal acceleration (m/s 2)
-6
1,0x10
… the most important in the MPO
orbit reconstruction …
5,0x10-7
0,0
-5,0x10-7
-1,0x10-6
-1,5x10-6
0
5000
10000
15000
20000
25000
Time (seconds)
The perturbing effect at the
orbital period (2.3 h) is about
2 orders–of–magnitude
larger than the
accelerometer accuracy of
 108 m/s2
V. Iafolla
100
108 m/s2
No modelling of the solar radiation
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Albedo: Radial acceleration
5x10-8
3 orbital periods  7 hours
1 Orbital period
Radial acceleration (m/s 2)
4x10-8
3x10-8
2x10-8
108 m/s2
1x10-8
2?
0
0
5000
10000
15000
20000
25000
Time (seconds)
The perturbing effect at the
orbital period (2.3 h) is only
a factor 2 larger than the
accelerometer accuracy of
 108 m/s2
No modelling of the albedo radiation
V. Iafolla
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26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Albedo: Transversal acceleration
Transversal acceleration (m/s 2)
4,0x10-9
108 m/s2
2,0x10-9
0,0
-2,0x10-9
-4,0x10-9
0
5000
10000
15000
20000
25000
Time (seconds)
The perturbing effect at the
orbital period (2.3 h) is
smaller than the
accelerometer accuracy of
 108 m/s2
No modelling of the albedo radiation
V. Iafolla
1ST MORE TEAM MEETING
26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
RSE total noise
V. Iafolla
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA accuracy requirement inside the frequency band
Frequency Hz
Acceleration values m / s 2 / Hz
V. Iafolla
3  10 5
10 4  10 3
10 1
3  10 8
10 8
10 7
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA General Description
ISA mechanical oscillator and its equivalence with a linear harmonic oscillator:
K
mr
Al 5056
I  t  kt  M
1
f0 
2
kt
 3.5Hz
I
mr x x  kx  F
f0 
1
2
k
 3.5Hz
mr
The accelerometer works at frequencies lower than the resonance frequency of the
mechanical oscillator, where the transfer function between the acceleration of the
sensitive mass and its displacement is: x   a2 
0
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA General Description
  2fp
•
The displacements of a proof–mass due to a perturbing acceleration are detected by
means of capacitive transducers in a bridge configuration, followed by a low noise
amplifier;
•
The capacitive bridge (CB) is biased at high frequency ( fp = 10 kHz ) so that
accelerations at frequencies fs produce their unbalance;
•
At the output of the CB the signals are seen as a modulation of the bias voltage at the
two side–bands f = fp  fs in the frequency domain;
V. Iafolla
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26-27 February 2007 Rome
ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Electrical and mechanical Parameters
amin
abw
ael
2
2
mr
fo
fp
P
C1
tg C1
Ca
tg Ca
vn
in
Tn


Qde
Qm
Q
V. Iafolla
ISA total intrinsic noise m / s 2 / Hz
Brownian noise (m / sec 2 ) 2 / Hz
Electronic noise (m / sec 2 ) 2 / Hz
Proof mass (Kg)
Frequency of resonance (Hz)
Polarisation frequency (KHz)
Pressure condition ( mbar )
Sensing capacity (pF)
Loss of C1
External fixed capacity (pF)
Loss of Ca
Electronic device
Voltage noise of amplifier ( V / Hz )
Current noise of amplifier ( A/ Hz )
Temperature noise of amplifier (K)
Transducer factor ( V / m )
Electromechanical transducer factor
Electric quality factor
Mechanical quality factor
Total quality factor
4.1*10 10
16 *10 20
1.5 *1021
0.22
3.5
10
10 2  10 3
300
4 * 10 4
300
3 *10 4
AD743/AD
3 * 10 9
7 * 10 15
0.76
10 5
3 *102
5.3 *10 4
10
10
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA General Description
ISA calibration
Electromechanical actuator
Superimposing an alternate voltage
to the constant voltage V
fe

C b
M 1  0 vV
d0 2
V. Iafolla
v  v0 cos(2f et )
2  fe

b C 2
M2 
v
2 d0
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Geophysical Measurements at the
Istituto Nazionale di Fisica Nucleare (INFN) Gran Sasso Laboratory
x 10
-3
Misure GEOSTAR
Earthquakes 13 gen 2001 17:33:29:22
Off Coast of Central America
Registrazione Gravimetro Geostar Ustica
-8.236
Accelerazione [g]
-8.238
-8.24
-8.242
-8.244
-8.246
12.74
Seismic Noise
12.75
12.76
12.77
12.78
Tempo giorni dal 2001
12.79
12.8
Teleseismic (free oscillation of Earth)
Solid tide of Earth
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Differential Accelerometer: Mechanical Arrangement
V. Iafolla
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26-27 February 2007 Rome
08/06/2006
Emiliano
Fiorenza
ALCATEL ALENIA
SPACE
ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Pick Up System
V. Iafolla
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26-27 February 2007 Rome
08/06/2006
Emiliano
Fiorenza
ALCATEL ALENIA
SPACE
ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Rejection: Electrical scheme
V. Iafolla
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26-27 February 2007 Rome
08/06/2006
Emiliano
Fiorenza
ALCATEL ALENIA
SPACE
ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Seismic Noise Rejection
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Vibrational random noise on board the MPO inside the frequency band
Frequency Hz
Acceleration values ( m / s 2 / Hz )
3 105
3 10 9
10 4  10 3 10 1
10 9
10 8
Micro-vibration random noise on board the MPO outside the frequency band
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Microvibration noise
ISA Block Diagram
f 0  3.5 Hz
Dynamic
Q  10
106
Ana log ic Filter
f cat 1 Hz
40 dB / dec
V. Iafolla
Dynamic
65536
Digital Filter
f cat  0.1 Hz
80 dB at 1Hz
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Positioning
(XYZ) represents the MPO frame with origin in COM;
(xyz) define the MPO position with respect to Mercury instantaneous orbital plane;
ZB
Z
Rotation axis

X
COM
ISA com
YB

Rt
XB

R0


R
Y
 



R  R0  R0  Rt (t )  Rt (t )
V. Iafolla
X–axis, along the radial direction
(Mercury–MPO radius vector);
Z–axis, along the out–of–plane
direction (perpendicular to the
orbital plane);
Y–axis, along the transversal
direction in the along–track
direction ( Xˆ  Yˆ  Zˆ );
ISA Gauss
frame
ISA LVLH
frame
X
Y
Z
ZLVLH XLVLH YLVLH
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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Positioning
This result suggest for the best configuration of the accelerometer a location with
the three sensitive masses aligned along the rotation axis of the MPO, and with the
com of the mass with sensitive axis along the rotation axis coincident with the com
of the accelerometer as well as with the MPO one:
comISA COM
Z–sensitive axis
Rotation axis
X–sensitive axis
Y–sensitive axis
V. Iafolla

 R0 X

 R0 Y

 R 0Z

 X
  0X
   Y0 X
 
  Z0X

X 0Y
Y0Y
Z 0Y
X 0 Z   0 0  5  10  2 

 
Y0 Z    0 0  5  10  2 

Z 0 Z   0 0
0

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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA mechanical configuration
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Positioning
Angular rate and angular acceleration
The angular rate and acceleration along the MPO axes are:
 X 

 
   Y 
    
Z 
 0
  X 

 
    Y 
    
Z 
 0
where 0 and  0 are the nominal values:
5


 0    n1  2e cos M  e 2 cos 2M  Oe 3 
2


 0    n 2  2e sin M  5e 2 sin 2M  Oe 3 
M  n
Satellite mean motion
  f 
f = true anomaly
where M represents the MPO mean anomaly around Mercury, and e  0.162
the MPO eccentricity;
V. Iafolla
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
Solution for the gravitational (tide) and apparent accelerations: general case
a ISA X


Z
2
2
2  4e cos M  5e 2 cos 2 M X x 
 3  10e cos M  5e  16e cos 2M X x 
n







 n2 
 2e sin M  5e 2 sin 2M X y  2Z X y 

n




X 
 Y
5 2


1

2
e
cos
M

e
cos
2
M

X


X
z
z



n 
2
n2


a ISAY



2e sin M  5e 2 sin 2 M Yx  2Z Yx 


n





1
5
5



2
Z 
 n 2  e cos M  e 2  e 2 cos 2 M  Y y  2
1

2
e
cos
M

e
cos
2
M

Y


y


2
2
n
2









Y 
 X
5 2


1

2
e
cos
M

e
cos
2
M

Y


Y


z
 z
n 
2
n2







a ISA Z
V. Iafolla




 Y
 X 

5 2


1

2
e
cos
M

e
cos
2
M

Z


Z

x
x



n 
2
n2


 Y 

 X
5 2

 n2  
1

2
e
cos
M

e
cos
2
M

Z


Z

y
y
2


n
2
n






3 2
9 2



1

e

3
e
cos
M

e
cos
2
M

Z


z


2
2




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Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Positioning
In order to determine the constraints in the possible displacements along the three
sensitive axes, we need to compare the previous formula with the accelerometer
accuracy:
A0  10 9 g   10 8 m / s 2
 



R  R0  R0  Rt (t )  Rt (t )
X0
V. Iafolla
Position ranges
0
Xt
±30 mm
Y0
0
Yt
±20 mm
Z0
0
Zt
±40 mm
±30 mm
±20 mm
±40 mm
Position accuracies
X 0
±4 mm
±5 mm
X t
±1 mm
Y0
±5.5 mm
Yt
±2 mm
Z 0
±11 mm
Z t
±4 mm
±7.5 mm
±15 mm
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Istituto Nazionale Di Astrofisica
Requirements on the angular rate and angular acceleration for the following fixed
values of the position of the spacecraft COM: Xt = 30 mm, Yt = 20 mm and Zt = 40 mm.

Case A)
1.34 10 5 rad s

1.76 10 8
rad s 2
Hz
Case B)
0.54  10 5 rad s
Hz
Hz
0.56  10 8
Hz
rad s 2
Case A: com ≡ COM
Case B: com +20 cm ≡ COM
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA thermal system overview
One of the main characteristics for the accelerometer to be considered in the
BepiColombo mission to Mercury is its thermal stability, i.e., the immunity of
the accelerometer to temperature variations:
over one orbital period (2.3 h) of the MPO;
 ±2 °C
over one sidereal period (44 days) of
 ±12.5 °C
Mercury;
 4 °C/Hz
Random noise;
8

In the actual version of the ISA accelerometer the thermal stability is: 5 10 g  / C
That is a temperature change of 1 degree produces a voltage output equivalent to:
5 10 8 g   5 10 7 m s 2
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Istituto Nazionale Di Astrofisica
ISA thermal system overview
GR=0,0067
COVER_BOX
ENVIROMENT
e0.9
GR=0,0005
OVEN BOX
ACCELEROMETER
PAKAGES
GL=0,3
GR=0,008
QI=0.078W
CONTROL
ELECTRONIC
THERMAL
INSULATOR
OVEN_PCB
GL=5
GL=0,003
QI = 3.7 W
GR=0,0028
GL=0,8
PCB QI=0.88W
GL=0.03
GL=0,5
GR=0,014
BOTTOM_BO GL=3
X
GR=0,05
SPACECRAFT
ISA Thermal Mathematical model
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ALCATEL ALENIA SPACE ITALIA
Istituto di Fisica dello Spazio Interplanetario
Istituto Nazionale Di Astrofisica
ISA Error Budget: Pseudo Sinusoidal Contributions
Type
Gravitygradients
Apparent
forces
Thermal
effects
Components
coupling
Total
Spectral
content
Orbital period
n
and ½P
0 ;  0 Orbital period
and ½P
Orbital period
2 °C
and ½P
Misalignment Orbital period
angle
and ½P
requirement Error %
on
A0
Due to
P


R0 ; Rt t 
85%A0
P
T
15%A0
P

Negligible
P
100%A0
"ISA accelerometer onboard the Mercury Planetary Orbiter: error budget“
Celestial Mech Dyn Astr DOI 10.1007/s10569-006-9059-0
http://dx.doi.org/10.1007/s10569-006-9059-0
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Istituto Nazionale Di Astrofisica
ISA Error Budget: Random Contributions
Type
Due to
 
R0 ; Rt t 
Apparent forces
4 C
Thermal effects
Noise on the MPO
MPO COM
displacement
Components
coupling
Error
percent
Random
 ; 
60%A0
Random
T
30%A0
Movements due to the
Random
HGA, fuel sloshing ecc.
Movements due to the
HGA
and
fuel Random
consumption ecc.
Misalignment angle
ISA intrinsic noise
Total (not correlated noise)
V. Iafolla
Hz
requirement
on
Spectral content
Random
Random
10%A0

Rt t 
70%A0

Negligible
Negligible
<100%A0
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ISA PAYLOAD OVERVIEW
ISA Detector Assy
ISA Control Electronics
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Istituto Nazionale Di Astrofisica
ISA DETECTOR ASSY OVERVIEW
External Shield
ISA Detector Assy
Electrical I/F
Accelerometer Thermal
Insulation
Internal Thermal shield
Accelerometer Package
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Istituto Nazionale Di Astrofisica
ISA Simulator (simulink)
ISA simulator diagram
Mechanical
Signal
Mechanical
noise
ISA
Mechanical
system
Output
Thermal noise
Input signal
Mechanical oscillator
V. Iafolla
ISA Thermal
system
Electro-mechanical system
Thermal system with active control
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ISA Signal and noise in the radial direction
ISA displacement:
[4cm+/-5mm; 4cm+/-7mm; 20cm+/-15mm]
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Integration
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Name / acronym
Italian Spring Accelerometer / ISA
Objectives
To measure the inertial acceleration acting on the MPO with high
precision. The scientific objectives are connected with those of the
RadioScience Experiment, i.e., a set of experiments that can give
information on the Mercury structure and to test Einstein’s theory of
General Relativity.
General
description
Three axes accelerometer with masses mechanically suspended by a
spring and with a capacitive transducer.
Units
N/A
Parameter
Reference P/L
N/A
N/A
Proof Mass Suspension
Transducer
Mechanical Parameter
Proof masses
Resonace frequency
Mechanical quality factor
Length of arms
Kg
Hz
//
m
Electrical Parameters
Detection capacitors.
Electrical loss in the detectors
capacitors
External fixed capacitors
noise
voltage
Equivalent
generator.
Equivalent
generator.
current
noise
Amplifier temperature noise
Transducer factor
Electromechanical
factor
Altitude
Pericenter precession
Periapsis longitude change
Phase angle
Value/Description
ISA-Italian Spring
Accelerometer
Mechanical
Capacitive
Remarks
Developed to the IFSI
0.22
3.5
10
45  10 3
300
pF
4 * 10 4
300
pF
V /
Hz
3 *10 9
A/
Hz
7 * 10 15
°K
V/m
0.38
10 5
3 * 10 2
Transducer
ORBIT
Inclination
Type of orbit
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Istituto Nazionale Di Astrofisica
.
N/A
km

°/orbit

Circular preferred,
elliptic acceptable
No requirement
No requirement
No requirement
No requirement
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CONFIGURATION
Units
Layout
Preferred location
#
N/A
N/A
Istituto Nazionale Di Astrofisica
COM
Thermal stabilized
area
PHYSICAL
Mass, total
Mass, mechanical part
Mass, electronics
Mass, harness
Dimension (mechanics)
Dimension (electronics)
kg
kg
kg
kg
mm
mm
POWER
Electronic power dissipation
Total Average power dissipation
Total Peak power dissipation
W
W
W
DATA RATE/VOLUME
Data volume
Data volume/orbit (nominal)
Data rate (nominal)
Data rate (burst)
Gbit
Gbit
Kbit/s
Kbit/s
POINTING
Pointing control APE
Attitude reconstruction AME
Pointing stability RPE
Alignment knowledge respect to
the MPO LVLH frame
Alignment stability
Co-Alignment w.r.t. other P/L
Co-Alignment Stability
THERMAL
Detector Assy
Detector Assy
Detector
Assy
I/F Orbital
stability
Detector
Assy
I/F sideral
stability
Electronic unit
Mechanical
stability
vs
temperature
Electronics
temperature
V. Iafolla
stability
vs
5.5
4
1.5
0.15+0.4/m
300 x 170x180
170x130x70
5.2
7.07
8.9
94.6
0.0125
1.5
80
arcsec
arcsec
arcsec
/8hours
mrad
0.3
mrad
mrad
mrad
Better than 0.3
Better than 0.3
Better than 0.3
C
C
C/orbit
-20;+45 TBC
-30;+55 TBC
+/-2
C/Mercu
ry year
°C
2
+/-12.5
-20;+45 TBC
7
m / s 2 / Hz
5  10 8
m / s / Hz
The location wrt the MPO COM is related to the knowledge of the
rotation state of the MPO. The accuracy in the knowledge of the
position of the proof masses must be 5mm in the zenith direction,
7mm along track and 15mm in the out of plane direction.
According to configuration layout
Baseline with active thermal control
Baseline with active thermal control
Baseline with active thermal control
According to operational modes
Without heather
Nominal power, with heather and in worst case condition
Peak power, with heather and in worst case condition
2 years
Filtered data
For TBD time
69
69
69
This value is determinate to the ISA dynamic
Operative range
Non Operative range
Operative range
5  10
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References
Bertotti, B., Iess, L., Tortora, P., A test of general relativity using radio links with the Cassini spacecraft, Lett. to Nature
425, 2003;
Fuligni, F., Iafolla, V., 1997. Measurement of small forces in the physics of gravitation and geophysics. Il Nuovo Cimento
20 C (5), 637–642;
Fuligni, F., Iafolla, V., Milyukov, V., Nozzoli, S., 1997. Experimental gravitation and geophysics. Il Nuovo Cimento 20 C
(5), 637–642;
Iafolla, V., Nozzoli, S., Mandiello, A., 1998. High sensitive accelerometer for fundamental physics in space. Second Joint
Meeting of the International Gravity Commission and the International Geoid Commission, Trieste, 7–12,
September;
Iafolla, V., Nozzoli, S., 2001. Italian spring accelerometer (ISA) a high sensitive accelerometer for ‘’BepiColombo‘’ ESA
CORNERSTONE. Plan. Space Science, 49, 1609–1617;
Iafolla, V., Lucchesi, D.M., Nozzoli, S., 2004. On the ISA accelerometer positioning inside the Mercury Planetary
Orbiter. Plan. and Space Scien., in press.
Milani, A, Vokrouhlicky, D., Villani, D., Bonanno, C., Rossi, A., Testing general relativity with the Bepicolombo radio
science experiment, Phs. Rev. D 66, 2002;
Milani A, Rossi, A., Villani, D., The BepiColombo Radio Science Simulations, Version 2, 11 April (2003);
V. Iafolla
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