The Revolution of the Moons of Jupiter - West Valley College
JUICE JUpiter ICy moons Explorer a L-class mission of ESA, … · 2016. 8. 4. · Contact:...
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Contact: [email protected] JUICE – JUpiter ICy moons Explorer a L-class mission of ESA, which will investigate and characterise Ganymede, Europa and Callisto as planetary objects and potential habitats [1], [2]. The current trajectory of JUICE foresees a flyby velocity of 4 km/s at Europa, other flybys are in the range of 1 up to 7 km/s and velocity in Ganymede orbits is around 2 km/s. Density enhancement model is given by following formula from [5] and is primary velocity and mass dependant: where n cs is the closed source number density, n os is the open source number density, T a the ambient gas temperature, T s the ion source temperature, is the cone half-angle of the open source, v sc the spacecraft velocity and its angle with respect to the entrance aperture and m the mass of the gas. Measured area ratio th-mode/n-mode is in good agreement with the density enhancement model for noble gases like Ne and Kr, as well as molecules like CH 4 , C 2 H 6 and C 3 H 8 and can be extrapolated for all JUICE mission phases. Behaviour of the antechamber (closed source) together with the NIM prototype could be successfully verified for gas beam velocities of 1 up to 4.5 km/s, which covers the majority of JUICE mission phases, including Europa flyby and Ganymede orbit. The verified mass range in n-mode and th-mode lasts from 2 (H 2 ) up to 84 amu (Kr), in which NIM would support up to 700 amu for a 20 s measurement. n-mode is expected to be independent with respect to the azimuthal entrance angle. This could be verified with the open source measurements ranging from -90° to +90°, which only show a damping of the signal with the mounting pillars in line of sight. The rest gas in the vacuum chamber is rotationally independent for both n-mode and th-mode, which is shown by the measurement of the rest gas species N 2 , CO, CO 2 and H 2 O in n-mode and th-mode. For the noble gases like Ne and Ar, its isotope abundance is compared with the natural table of isotopic abundances from [6]. The measured relative isotopic accuracy to natural abundance reaches from 100 ppm for 40 Ar in th-mode up to almost 1 for 36 Ar in n-mode, depending on the signal-to-noise ratio (SNR) up to the detection limit. n- mode and th-mode mean accuracies are shifted due to the density enhancement, which also results in a SNR enhancement and therefore a better accuracy for th-mode. th-mode is in space expected to be modulated by a cosine of the angle between entrance aperture of the antechamber and the spacecraft velocity. For the th-mode measurements, an additional modulation with the Gaussian gas beam profile is observed around +/-30°. Unexpected side-lobes occur with maxima at +/-45°, most probably due to scattering of the gas beam with the mounting screws of the antechamber. Moreover, the direct comparison of the n-mode (open source) and th-mode (closed source) gives no evidence for any fractionation effects inside the antechamber, since both modes measure almost the same composition, at least for the measured molecules H 2 , CH 4 , C 2 H 6 , C 3 H 8 , as well as Methanol vapour and Propanol vapour. For the molecules like C 3 H 8 (Propane), its isotope abundance is compared with the NIST electron ionization abundance from [7]. The measured mean relative isotopic accuracy to NIST electron ionization abundance is between 10 to 20% for both n-mode and th-mode, which is about the NIST measurement accuracy and suggests, together with the noble gas results, a much higher accuracy for the NIM prototype instrument. [1] ESA, “JUICE assessment study report (Yellow Book)”, ESA/SRE(2011)18, 2012. [2] O. Grasset et al., “JUpiter Icy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system”, Planet. Space Sci., 2013, 78, pp. 1 – 21. [5] M. Wüest, D.S. Evans, R. von Steiger, “Calibration of Particle Instruments in Space Physics“, International Space Science Institute, ISBN: 987-92-9221-936-9, 2007. NIM prototype is successfully tested under realistic JUICE mission conditions. n-mode (open source) and th-mode (closed source) measure almost the same composition for noble gases, as well as for molecules, indicating no additional fragmentation of the species inside the antechamber. NIM (Neutral gas and Ion Mass spectrometer) is a time-of-flight instrument with heritage from the RTOF sensor of the ROSINA instrument on the Rosetta mission [3] and the P-BACE instrument [4]. NIM can be operated in 3 different modes: th-mode, n-mode and i-mode, to measure the chemical composition of the inflowing neutral gas, as well as direct ions from the exospheres of the icy Jovian moons. Ion (i-)mode (open source): ions (i + ) enter the ion-source with spacecraft velocity and are directly guided through ion-optics to the detector, used for thermal ion measurements close to the moon (orbit or closest approach at flyby). Thermal (th-)mode (closed source): neutrals (th 0 ) get thermally accommodated to wall temperature by several collisions inside an equilibrium sphere (antechamber) before entering the ion source and are then ionized by an electron beam, used for neutral gas measurements at any mission phase, mainly at Europa torus crossing and all other flybys. Neutral (n-)mode (open source): neutrals (n 0 ) enter the ion source with spacecraft velocity and are then ionized by an electron beam, used for neutral gas measurements close to the moon (orbit or closest approach at flyby). PEP – Particle Environment Package carried by JUICE combines remote global imaging with in-situ measurements to study the atmospheres, plasma environments, and magnetospheric interactions and determine global surface compositions and chemistry, especially as related to habitability. (PI: S. Barabash, Swedish Institute of Space Physics, Kiruna, Sweden, Co-PI: P. Wurz, University of Bern, Switzerland) We developed a prototype of the NIM, part of PEP for the JUICE mission and performed measurements with the prototype instrument using a neutral gas beam of 1 up to 5 km/s velocity, containing different species in the neutral (open source) and thermal (closed source) mode. The results of these measurements with respect to fragmentation and density enhancements in the closed source mode are presented here. Furthermore, we give a direct comparison between open and closed source mode measurements. NIM – Neutral gas and Ion Mass spectrometer is part of PEP and will be used to measure the chemical composition of regular atmosphere produced by energetic particle and photon interaction with the surface of the icy Jovian moons (volatiles, contribution from non-ice material on the surface and isotopic composition of major species), as well as the ion composition of the ionospheres. We performed measurements with the prototype NIM using a neutral gas beam of realistic velocities in the n-mode (open source) and th-mode (closed source). To obtain a neutral gas beam at such velocities, the CASYMIR (CAlibration SYstem for the Mass spectrometer Instrument Rosina) facility has been used. Different species and mixtures are used, such as noble gases Ne, Ar, Kr as well as molecules like H 2 , CH 4 , C 2 H 6 , C 3 H 8 and more complex ones. Measurement characteristics: Beam: ~ 10 -9 mbar of gas, Gaussian profile with sigma ~ 10 mm at instrument entrance, velocity 1 up to 4.5 km/s. th-mode: antechamber (closed source) of 40 mm diameter with 4 mm entrance hole and DLC-coated inside (Gold-coated is also tested) with mounting screws at +/-45° from 0°-position, ionizing electron beam of 100 A. n-mode: line-of-sight (open source) entrance 2 mm x 6 mm with mounting pillars of 4 mm every 30°, ionizing electron beam of 100 A. Rest gas: ~ 10 -10 mbar of rest gas in the UHV-chamber, mainly N 2 , H 2 O, CO, CO 2 . Azimuthal rotation campaign: measurement of the gas mixtures at different azimuthal entrance angles (+/-90° from 0°-position) for both n-mode and th-mode, at the same velocity for each gas mixture (2 up to 3 km/s) Velocity campaign: measurement of the gas mixtures at different velocities (1 up to 4.5 km/s) for both n-mode and th-mode, at 0°-position. Antechamber (closed source) behaves as expected with predictable density enhancement over the specified mass range and within the JUICE mission phase velocities. [6] J.S. Becker, “Inorganic Mass Spectrometry: Principles and Applications, Appendix I”, John Wiley & Sons, ISBN: 978-0-470-01200-0, 2007. [7] NIST Standard Reference Database, “http://webbook.nist.gov/chemistry/”, National Institute of Standards and Technology, 2016. [4] D. Abplanalp, P. Wurz, L. Huber, I. Leya, E. Kopp, U. Rohner, M. Wieser, L. Kalla, and S. Barabash, “A neutral gas mass spectrometer to measure the chemical composition of the stratosphere”, Adv. Space Res. 44 (7) 870–878, 2009. [3] H. Balsiger et al., “ROSINA – ROSETTA ORBITER SPECTROMETER FOR ION AND NEUTRAL ANALYSIS”, Space Sci. Rev., 128 (1-4) 745-801, 2007. NIM prototype NIM scheme CASYMIR calibration facility NIM instrument gas entrance scheme for both th-mode and n-mode 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 0 0.2 0.4 0.6 0.8 1 Ne Ar Isotopic mass number [amu] Measured isotope abundance [1] Natural isotope abund. for Ne / Ar n-mode abund. for Ne / Ar th-mode abund. for Ne / Ar 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 0 0.4 0.8 1.2 1.6 2 2.4 Isotopic mass number [amu] Area norm. to ref. isotope [1] NIST e-ionization abundance for C3H8 Isotopic interference n-mode abundance for C3H8 th-mode abundance for C3H8 18 20 22 24 26 28 30 32 34 36 38 40 42 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 Ne Ar Mean Mean Isotopic mass number [amu] Rel. accuracy to natural abundance [1] n-mode, Ne / Ar th-mode, Ne / Ar 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 10 -5 10 -4 10 -3 10 -2 10 -1 10 0 Mean Isotopic mass number [amu] Rel. accuracy to NIST [1] n-mode, C3H8 th-mode, C3H8 -90 -60 -30 0 30 60 90 0 5 10 15 20 25 pillar pos. pillar pos. Azimuthal entrance angle [°] n-mode: Species area / 10 -9 mbar [a.u.] Ne Ar Kr C2H6 C3H8 -90 -60 -30 0 30 60 90 0 50 100 150 200 screw pos. screw pos. Azimuthal entrance angle [°] th-mode: Species area / 10 -9 mbar [a.u.] Ne Ar Kr C2H6 C3H8 -90 -60 -30 0 30 60 90 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 Azimuthal entrance angle [°] n-mode: Species area / 10 -9 mbar [a.u.] N2 CO CO2 H2O -90 -60 -30 0 30 60 90 0 0.05 0.1 0.15 0.2 Azimuthal entrance angle [°] th-mode: Species area / 10 -9 mbar [a.u.] N2 CO CO2 H2O 0.5 1 1.5 2 2.5 3 3.5 4 4.5 0 4 8 12 16 20 Density enhancement model Beam velocity [km/s] Ratio th-/n-mode area / 10 -9 mbar [a.u.] H2 Ne Kr C3H8 0 10 20 30 40 50 60 70 80 90 0 4 8 12 16 20 24 H2 CH4 Ne C2H6 C3H8 Kr Density enhancement model Species mass [amu] Ratio th-/n-mode area / 10 -9 mbar [a.u.] v = 1.1 km/s v = 1.7 km/s v = 2.3 km/s v = 2.7 km/s v = 3.2 km/s v = 3.7 km/s
Transcript of JUICE JUpiter ICy moons Explorer a L-class mission of ESA, … · 2016. 8. 4. · Contact:...
Contact: [email protected]
JUICE – JUpiter ICy moons Explorer a L-class mission of ESA, which will investigate and characterise Ganymede, Europa and Callisto as planetary objects and potential habitats [1], [2]. The current trajectory of JUICE foresees a flyby velocity of 4 km/s at Europa, other flybys are in the range of 1 up to 7 km/s and velocity in Ganymede orbits is around 2 km/s.
Density enhancement model is given by following formula from [5] and is primary velocity and mass dependant:
where ncs is the closed source number density, nos is the open source number density, Ta the ambient gas temperature, Ts
the ion source temperature, is the cone half-angle of the open source, vsc the spacecraft velocity and its angle with respect to the entrance aperture and m the mass of the gas.
Measured area ratio th-mode/n-mode is in good agreement with the density enhancement model for noble gases like Ne and Kr, as well as molecules like CH4, C2H6 and C3H8 and can be extrapolated for all JUICE mission phases.
Behaviour of the antechamber (closed source) together with the NIM prototype could be successfully verified for gas beam velocities of 1 up to 4.5 km/s, which covers the majority of JUICE mission phases, including Europa flyby and Ganymede orbit.
The verified mass range in n-mode and th-mode lasts from 2 (H2) up to 84 amu (Kr), in which NIM would support up to 700 amu for a 20 s measurement.
n-mode is expected to be independent with respect to the azimuthal entrance angle. This could be verified with the open source measurements ranging from -90° to +90°, which only show a damping of the signal with the mounting pillars in line of sight.
The rest gas in the vacuum chamber is rotationally independent for both n-mode and th-mode, which is shown by the measurement of the rest gas species N2, CO, CO2 and H2O in n-mode andth-mode.
For the noble gases like Ne and Ar, its isotope abundance is compared with the natural table of isotopic abundances from [6]. The measured relative isotopic accuracy to natural abundance reaches from 100 ppm for 40Ar in th-mode up to almost 1 for 36Ar in n-mode, depending on the signal-to-noise ratio (SNR) up to the detection limit. n-mode and th-mode mean accuracies are shifted due to the density enhancement, which also results in a SNR enhancement and therefore a better accuracy for th-mode.
th-mode is in space expected to be modulated by a cosine of the angle between entrance aperture of the antechamber and the spacecraft velocity. For the th-mode measurements, an additional modulation with the Gaussian gas beam profile is observed around +/-30°. Unexpected side-lobes occur with maxima at +/-45°, most probably due to scattering of the gas beam with the mounting screws of the antechamber.
Moreover, the direct comparison of the n-mode (open source) and th-mode (closed source) gives no evidence for any fractionation effects inside the antechamber, since both modes measure almost the same composition, at least for the measured molecules H2, CH4, C2H6, C3H8, as well as Methanol vapour and Propanol vapour.
For the molecules like C3H8 (Propane), its isotope abundance is compared with the NIST electron ionization abundance from [7]. The measured mean relative isotopic accuracy to NIST electron ionization abundance is between 10 to 20% for both n-mode and th-mode, which is about the NIST measurement accuracy and suggests, together with the noble gas results, a much higher accuracy for the NIM prototype instrument.
[1] ESA, “JUICE assessment study report (Yellow Book)”, ESA/SRE(2011)18, 2012.
[2] O. Grasset et al., “JUpiter Icy moons Explorer (JUICE): An ESA mission to orbit Ganymede and to characterise the Jupiter system”, Planet. Space Sci., 2013, 78, pp. 1 – 21.
[5] M. Wüest, D.S. Evans, R. von Steiger, “Calibration of Particle Instruments in Space Physics“, International Space Science Institute, ISBN: 987-92-9221-936-9, 2007.
NIM prototype is successfully tested under realistic JUICE mission conditions.
n-mode (open source) and th-mode (closed source) measure almost the same composition for noble gases, as well as for molecules, indicating no additional fragmentation of the species inside the antechamber.
NIM (Neutral gas and Ion Mass spectrometer) is a time-of-flight instrument with heritage from the RTOF sensor of the ROSINA instrument on the Rosetta mission [3] and the P-BACE instrument [4].
NIM can be operated in 3 different modes: th-mode, n-mode and i-mode, to measure the chemical composition of the inflowing neutral gas, as well as direct ions from the exospheres of the icy Jovian moons.
Ion (i-)mode (open source): ions (i+) enter the ion-source with spacecraft velocity and are directly guided through ion-optics to the detector, used for thermal ion measurements close to the moon (orbit or closest approach at flyby).
Thermal (th-)mode (closed source): neutrals (th0) get thermally accommodated to wall temperature by several collisions inside an equilibrium sphere (antechamber) before entering the ion source and are then ionized by an electron beam, used for neutral gas measurements at any mission phase, mainly at Europa torus crossing and all other flybys.
Neutral (n-)mode (open source): neutrals (n0) enter the ion source with spacecraft velocity and are then ionized by an electron beam, used for neutral gas measurements close to the moon (orbit or closest approach at flyby).
PEP – Particle Environment Package carried by JUICE combines remote global imaging with in-situ measurements to study the atmospheres, plasma environments, and magnetospheric interactions and determine global surface compositions and chemistry, especially as related to habitability.(PI: S. Barabash, Swedish Institute of Space Physics, Kiruna, Sweden,Co-PI: P. Wurz, University of Bern, Switzerland)
We developed a prototype of the NIM, part of PEP for the JUICE mission and performed measurements with the prototype instrument using a neutral gas beam of 1 up to 5 km/s velocity, containing different species in the neutral (open source) and thermal (closed source) mode. The results of these measurements with respect to fragmentation and density enhancements in the closed source mode are presented here. Furthermore, we give a direct comparison between open and closed source mode measurements.
NIM – Neutral gas and Ion Mass spectrometer is part of PEP and will be used to measure the chemical composition of regular atmosphere produced by energetic particle and photon interaction with the surface of the icy Jovian moons (volatiles, contribution from non-ice material on the surface and isotopic composition of major species), as well as the ion composition of the ionospheres.
We performed measurements with the prototype NIM using a neutral gas beam of realistic velocities in the n-mode (open source) and th-mode (closed source). To obtain a neutral gas beam at such velocities, the CASYMIR (CAlibration SYstem for the Mass spectrometer Instrument Rosina) facility has been used. Different species and mixtures are used, such as noble gases Ne, Ar, Kr as well as molecules like H2, CH4, C2H6, C3H8
and more complex ones.
Measurement characteristics:Beam: ~ 10-9 mbar of gas, Gaussian profile with sigma ~ 10 mm at instrument entrance, velocity 1 up to 4.5 km/s.th-mode: antechamber (closed source) of 40 mm diameter with 4 mm entrance hole and DLC-coated inside (Gold-coated is also tested) with mounting screws at +/-45° from 0°-position, ionizing electron beam of 100 A.n-mode: line-of-sight (open source) entrance 2 mm x 6 mm with mounting pillars of 4 mm every 30°, ionizing electron beam of 100 A.Rest gas: ~ 10-10 mbar of rest gas in the UHV-chamber, mainly N2, H2O, CO, CO2.Azimuthal rotation campaign: measurement of the gas mixtures at different azimuthal entrance angles (+/-90° from 0°-position) for both n-mode and th-mode, at the same velocity for each gas mixture (2 up to 3 km/s)Velocity campaign: measurement of the gas mixtures at different velocities (1 up to 4.5 km/s) for both n-mode and th-mode, at 0°-position.
Antechamber (closed source) behaves as expected with predictable density enhancement over the specified mass range and within the JUICE mission phase velocities.
[6] J.S. Becker, “Inorganic Mass Spectrometry: Principles and Applications, Appendix I”, John Wiley & Sons, ISBN: 978-0-470-01200-0, 2007.
[7] NIST Standard Reference Database, “http://webbook.nist.gov/chemistry/”, National Institute of Standards and Technology, 2016.
[4] D. Abplanalp, P. Wurz, L. Huber, I. Leya, E. Kopp, U. Rohner, M. Wieser, L. Kalla, and S. Barabash, “A neutral gas mass spectrometer to measure the chemical composition of the stratosphere”, Adv. Space Res. 44 (7) 870–878, 2009.
[3] H. Balsiger et al., “ROSINA – ROSETTA ORBITER SPECTROMETER FOR ION AND NEUTRAL ANALYSIS”, Space Sci. Rev., 128 (1-4) 745-801, 2007.
NIM prototype
NIM scheme
CASYMIR calibration facility
NIM instrument gas entrance scheme for both th-mode and n-mode
12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 460
0.2
0.4
0.6
0.8
1 Ne Ar
Isotopic mass number [amu]
Mea
sure
d is
otop
e ab
unda
nce
[1]
Natural isotope abund. for Ne / Arn-mode abund. for Ne / Arth-mode abund. for Ne / Ar
12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 460
0.4
0.8
1.2
1.6
2
2.4
Isotopic mass number [amu]
Are
a no
rm. t
o re
f. is
otop
e [1
]
NIST e-ionization abundance for C3H8Isotopic interferencen-mode abundance for C3H8th-mode abundance for C3H8
18 20 22 24 26 28 30 32 34 36 38 40 4210-5
10-4
10-3
10-2
10-1
100
Ne Ar
Mean
Mean
Isotopic mass number [amu]
Rel
. acc
urac
y to
nat
ural
abu
ndan
ce [1
]
n-mode, Ne / Ar th-mode, Ne / Ar
14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 4410-5
10-4
10-3
10-2
10-1
100
Mean
Isotopic mass number [amu]
Rel
. acc
urac
y to
NIS
T [1
]
n-mode, C3H8 th-mode, C3H8
-90 -60 -30 0 30 60 900
5
10
15
20
25
pillar pos. pillar pos.
Azimuthal entrance angle [°]
n-m
ode:
Spe
cies
are
a / 1
0-9 m
bar [
a.u.
]
Ne Ar Kr C2H6 C3H8
-90 -60 -30 0 30 60 900
50
100
150
200
screw pos. screw pos.
Azimuthal entrance angle [°]
th-m
ode:
Spe
cies
are
a / 1
0-9 m
bar [
a.u.
]
Ne Ar Kr C2H6 C3H8
-90 -60 -30 0 30 60 900
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Azimuthal entrance angle [°]
n-m
ode:
Spe
cies
are
a / 1
0-9 m
bar [
a.u.
]
N2 CO CO2 H2O
-90 -60 -30 0 30 60 900
0.05
0.1
0.15
0.2
Azimuthal entrance angle [°]
th-m
ode:
Spe
cies
are
a / 1
0-9 m
bar [
a.u.
]
N2 CO CO2 H2O
0.5 1 1.5 2 2.5 3 3.5 4 4.50
4
8
12
16
20
Density enhancement model
Beam velocity [km/s]
Rat
io th
-/n-m
ode
area
/ 10
-9 m
bar [
a.u.
]
H2 Ne Kr C3H8
0 10 20 30 40 50 60 70 80 90
0
4
8
12
16
20
24H2 CH4 Ne C2H6 C3H8 Kr
Density enhancement model
Species mass [amu]
Rat
io th
-/n-m
ode
area
/ 10
-9 m
bar [
a.u.
]
v = 1.1 km/s v = 1.7 km/s v = 2.3 km/s v = 2.7 km/s v = 3.2 km/s v = 3.7 km/s
