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Proposed optical observations of Comet Halley
Adv. Space Res. Vol.4 No. 9, pp.311—313, 1984 Printed in Great Britain. All rights reserved.
0273—1177/84 $0.00 + .50 Copyright © COSPAR
PROPOSED OPTICAL OBSERVATIONS OF COMET HALLEY S. Rath,* D. Jadhav,** P. Choudhary*** and A. Tillu* Department of Physics, University of Poona, Pune-7, India *Indian Institute of Tropical Meteorology, Pune-8, India * * * Department of Physics, Ahmednagar College, Ahmednagar,
*
*
India
ABSTRACT
A comprehensive programme is proposed for optical observations of Comet Halley based on the wide range of available facilities such as photometers, monochromators, interferometers and a polarimeter. Feasibility study of the proposed investigations with reference to existing facilities is carried Out for each technique and needs for additional instrumentation are established. Conclusions for optimum utilization of existing facilities are presented. INTRODUCTION Investigations of several optical phenomena in the area of Space and Atmospheric Physics have been carried out at Pune, since the last decade or so and the following facilities are presently operational. Photometers 1. 2. 3.
Four Colour Extinction Photometer (EP) All Sky Scanning Four Colour Night Airglow Photometer (AP) Zeeman Photometer for Sodium Dayglow (ZP)
thnochromators and the Polarimeter 4. 5. 6.
Double Diffraction t~bnochromator (DUN)
Czerny Turner l~bnochromator (CTM) Spectral Scanning Polarimeter (SSP)
As a part of worldwide Middle Atmosphere Programme (MAP), the following additional facilities are being developed and are expected to be operational towards the end of December 1984. Photometers 7.
Three Channel Twin Photometer (TCTP)
Interferometers 8. 9. 10.
Spherical Fabry Perot Interferometer for sodium lines (SFPI 5893) Spherical Fabry Perot Interferometer for 5577 line (SFPI 5577) Plane Fabry Perot Interferometer for 6300 line (PFPI 6300)
It is proposed to use the above range of facilities for optical observations of Comet Halley. PROPOSED PLAN OF INVESTIGATION A rapid preliminary survey /1/ suggested that the following investigations are possible. Photometric ~asurements Photometry of bright cometary emissions Depopulation and recycling study of known species Scanning of cometary profile
311
312
S. Rath et al.
Spectrophotometric Measurements Determination of excess colour in cometary scattered radiation Nigh resolution studies of weaker and unknown species Rotational Structure studies Simultaneous monitoring of solar activity in specific emissions Tail spectra of cometary ions Interferometric Measurements Condensation velocities by Doppler technique Line widths of specific emissions Polarimetric ~easurements Polarization of scattered continuum Polarization of emission lines FEASIBILITY STUDIES The feasibility studies were carried out for each proposed investigation using the following general criteria: (i) Whether the available instrument has the necessary capability e.g. wavelength resolution, light gathering power, temporal and spatial resolution etc. for the suggested investigation. (ii) What additional instrumentation is necessary to make the investigation possible? (iii) Is the investigation possible without a telescope? If a telescope is needed what is the minimum size of telescope that will suffice? (iv) Will it be possible to develop the remaining instrumentation within the limited time that is still available? What additional resources are required? The detailed discussion of
such feasibility studies has
recently been compiled /1/.
We
therefore present here only the final results. RESULTS
1. ti~nochromators and the polarimeter have the necessary capabilities only for wavelength and temporal resolution. But they can be used with a telescope. The telescope required should have a mirror of minimum diameter of 45 cm. The required electronic data acquisition has already been under development for the present NAP applications /2/. However there does not exist any telescope of the required size. Such a telescope needs to be acquired. 2. The interferometers are not yet operational. Buth their projected capability would be enough only if they are combined with a similar telescope. 3. The photometers are more promising. With some adjustments and improvements these can be used for the proposed investigations even without a telescope. Out of the range of the photometers which are available, the Three Channel Twin Photometer has a maximum flexibility in wavelength, as well as in temporal and spatial resolution, and is thus best adaptable for the cometary investigation. DISCUSSION It has thus become apparent that without the telescope (or telescopes) most of the investigations proposed above for Comet Halley are not possible. We presently have a capability of producing mirrors of diameter of 15 cm as used in our instruments CTN sun SSP. A design of Multiple ~arror Telescope (1~iflT) using seven mirrors in a honey—comb pattern is under active consideration and seems more feasible than making a large mirror of 45 cm diameter. But within the limited time and resources that are presently available, at the best only one such telescope can be developed. Hence we have to be selective in choosing the investigation. Mereover the present investigations in the Middle Atmosphere may need further observations and cannot be abruptly suspended. An adequate integration of present and new interests is therefore necessary. In the last few years we have concentrated mainly on monitoring atmospheric sodium on a round—the—clock basis /2/. A meteoritic origin of atmospheric sodium is nowadays more seriously considered and pursued /3/. Similarly, comets have been studied as a source of sodium /4/. We accordingly propose to reorient our present investigations towards “Cometary and Meteoritic origin of sodium,” with observations of Comet Halley as our first opportunity. Our reoriented observational programme would therefore be as follows: 1. Atmospheric sodium will be monitored with most of the present facilities as at present, before, during and after the period of visit of Comet Halley.
Optical Observations of Comet Halley
313
2. Sodium emission in Comet Halley will be monitored using TCTP. It will also possibly be monitored interferometrically in conjunction with the proposed HIlT. (Additional measurements would be contemplated only if more resources are available.) 3. The above programme would be complemented by adding a Twin Channel All Sky instrument for simultaneous monitoring of meteors on a TV channel and sodium night airgiow in a photometer channel. A feasibility study of such a system has also been completed recently /5/. REFERENCES
1. 2. 3. 4. 5.
5. Rath, Halley’s Comet, Project Report for Ii.Sc. Degree, Department of Physics, Univ. Poona, Pune, India (April 1984). M.R. Tade and A.D. Tillu, Ring effect and sodium dayglow, Symposium 5, “First Achievements of MAP,’ Adv. Space Res., in press (1984) W.J. Baggaley, Meteors and Aeronomy, Rep. Astron. 18A, 229—230 (1982) M. Oppenheimer, Sodium D—line emission in Comet West (1975n) and the sodium sources in comets. Astrophys. J. 240, 923—928 (1980). D. Angal, Meteoritic Origin of Sodium, Project Report for M.Sc. Degree, Department of Physics, Univ. Poona, Pune, India (April 1984).
0273—1177/84 $0.00 + .50 Copyright © COSPAR
PROPOSED OPTICAL OBSERVATIONS OF COMET HALLEY S. Rath,* D. Jadhav,** P. Choudhary*** and A. Tillu* Department of Physics, University of Poona, Pune-7, India *Indian Institute of Tropical Meteorology, Pune-8, India * * * Department of Physics, Ahmednagar College, Ahmednagar,
*
*
India
ABSTRACT
A comprehensive programme is proposed for optical observations of Comet Halley based on the wide range of available facilities such as photometers, monochromators, interferometers and a polarimeter. Feasibility study of the proposed investigations with reference to existing facilities is carried Out for each technique and needs for additional instrumentation are established. Conclusions for optimum utilization of existing facilities are presented. INTRODUCTION Investigations of several optical phenomena in the area of Space and Atmospheric Physics have been carried out at Pune, since the last decade or so and the following facilities are presently operational. Photometers 1. 2. 3.
Four Colour Extinction Photometer (EP) All Sky Scanning Four Colour Night Airglow Photometer (AP) Zeeman Photometer for Sodium Dayglow (ZP)
thnochromators and the Polarimeter 4. 5. 6.
Double Diffraction t~bnochromator (DUN)
Czerny Turner l~bnochromator (CTM) Spectral Scanning Polarimeter (SSP)
As a part of worldwide Middle Atmosphere Programme (MAP), the following additional facilities are being developed and are expected to be operational towards the end of December 1984. Photometers 7.
Three Channel Twin Photometer (TCTP)
Interferometers 8. 9. 10.
Spherical Fabry Perot Interferometer for sodium lines (SFPI 5893) Spherical Fabry Perot Interferometer for 5577 line (SFPI 5577) Plane Fabry Perot Interferometer for 6300 line (PFPI 6300)
It is proposed to use the above range of facilities for optical observations of Comet Halley. PROPOSED PLAN OF INVESTIGATION A rapid preliminary survey /1/ suggested that the following investigations are possible. Photometric ~asurements Photometry of bright cometary emissions Depopulation and recycling study of known species Scanning of cometary profile
311
312
S. Rath et al.
Spectrophotometric Measurements Determination of excess colour in cometary scattered radiation Nigh resolution studies of weaker and unknown species Rotational Structure studies Simultaneous monitoring of solar activity in specific emissions Tail spectra of cometary ions Interferometric Measurements Condensation velocities by Doppler technique Line widths of specific emissions Polarimetric ~easurements Polarization of scattered continuum Polarization of emission lines FEASIBILITY STUDIES The feasibility studies were carried out for each proposed investigation using the following general criteria: (i) Whether the available instrument has the necessary capability e.g. wavelength resolution, light gathering power, temporal and spatial resolution etc. for the suggested investigation. (ii) What additional instrumentation is necessary to make the investigation possible? (iii) Is the investigation possible without a telescope? If a telescope is needed what is the minimum size of telescope that will suffice? (iv) Will it be possible to develop the remaining instrumentation within the limited time that is still available? What additional resources are required? The detailed discussion of
such feasibility studies has
recently been compiled /1/.
We
therefore present here only the final results. RESULTS
1. ti~nochromators and the polarimeter have the necessary capabilities only for wavelength and temporal resolution. But they can be used with a telescope. The telescope required should have a mirror of minimum diameter of 45 cm. The required electronic data acquisition has already been under development for the present NAP applications /2/. However there does not exist any telescope of the required size. Such a telescope needs to be acquired. 2. The interferometers are not yet operational. Buth their projected capability would be enough only if they are combined with a similar telescope. 3. The photometers are more promising. With some adjustments and improvements these can be used for the proposed investigations even without a telescope. Out of the range of the photometers which are available, the Three Channel Twin Photometer has a maximum flexibility in wavelength, as well as in temporal and spatial resolution, and is thus best adaptable for the cometary investigation. DISCUSSION It has thus become apparent that without the telescope (or telescopes) most of the investigations proposed above for Comet Halley are not possible. We presently have a capability of producing mirrors of diameter of 15 cm as used in our instruments CTN sun SSP. A design of Multiple ~arror Telescope (1~iflT) using seven mirrors in a honey—comb pattern is under active consideration and seems more feasible than making a large mirror of 45 cm diameter. But within the limited time and resources that are presently available, at the best only one such telescope can be developed. Hence we have to be selective in choosing the investigation. Mereover the present investigations in the Middle Atmosphere may need further observations and cannot be abruptly suspended. An adequate integration of present and new interests is therefore necessary. In the last few years we have concentrated mainly on monitoring atmospheric sodium on a round—the—clock basis /2/. A meteoritic origin of atmospheric sodium is nowadays more seriously considered and pursued /3/. Similarly, comets have been studied as a source of sodium /4/. We accordingly propose to reorient our present investigations towards “Cometary and Meteoritic origin of sodium,” with observations of Comet Halley as our first opportunity. Our reoriented observational programme would therefore be as follows: 1. Atmospheric sodium will be monitored with most of the present facilities as at present, before, during and after the period of visit of Comet Halley.
Optical Observations of Comet Halley
313
2. Sodium emission in Comet Halley will be monitored using TCTP. It will also possibly be monitored interferometrically in conjunction with the proposed HIlT. (Additional measurements would be contemplated only if more resources are available.) 3. The above programme would be complemented by adding a Twin Channel All Sky instrument for simultaneous monitoring of meteors on a TV channel and sodium night airgiow in a photometer channel. A feasibility study of such a system has also been completed recently /5/. REFERENCES
1. 2. 3. 4. 5.
5. Rath, Halley’s Comet, Project Report for Ii.Sc. Degree, Department of Physics, Univ. Poona, Pune, India (April 1984). M.R. Tade and A.D. Tillu, Ring effect and sodium dayglow, Symposium 5, “First Achievements of MAP,’ Adv. Space Res., in press (1984) W.J. Baggaley, Meteors and Aeronomy, Rep. Astron. 18A, 229—230 (1982) M. Oppenheimer, Sodium D—line emission in Comet West (1975n) and the sodium sources in comets. Astrophys. J. 240, 923—928 (1980). D. Angal, Meteoritic Origin of Sodium, Project Report for M.Sc. Degree, Department of Physics, Univ. Poona, Pune, India (April 1984).