Planetary Astronomy; an Appraisal of Ground-Based Opportunities (1968) / Chapter Skim
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Observational Techniques and Facilities
Observational Techniques and Facilities
Pages 46-63
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From page 46... ...
It also surveys the major optical, radio, and radar facilities with capabilities for planetary research. RADIO AND RADAR TARGET MAPPING TECHNIQUES The relatively long wavelength of radio and radar observing systems as compared with optical telescopes makes it difficult to obtain a high degree of angular resolution of the target by the straightforward use of large reflectors alone.
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From page 47... ...
The signal-to-noise ratio obtained from these "unfilled" apertures will be considerably lower than that produced by a filled aperture in the same observation time, but for many targets useful results can still be obtained. For radar observations of a rigid body, there is even greater redundancy in the returning signal, since the echoes represent the scattering of a coherent transmission by a collection of scattering elements maintaining a fixed relationship to one another.
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From page 48... ...
A, North lunar pole; B, pole of apparent rotation; D, Doppler contour for relative frequency, /; R, range contour for relative range, t. Figure 3.
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From page 49... ...
For baselines up to a few hundred kilometers, the individual elements of an interferometer or array can be connected by cables or radio links. The high-resolution arrays planned for the Owens Valley Radio Observatory and the National Radio Astronomy Observatory are designed to give resolution to a few seconds of arc at wavelengths over the 3- to 21-cm range using a number of moderatesized reflectors interconnected by cables.
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From page 50... ...
However, because of the great detail obtained and the high precision of wavelength measurement, the data provide a unique and nearly complete picture, both qualitatively and quantitatively, of the planetary atmospheric constituents outside of the telluric bands. It is true, of course, that only gases having infrared-active vibrations or a sufficiently large quadrupole moment can be observed.
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From page 51... ...
Insert: atmospheric window from 16 to 24 /j, observed by Adel at Flagstaff, Arizona. The total precipitable water was about 2 mm, and the cutoff of the KBr prism was near 24 /*
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From page 52... ...
by H2 and by He on Jupiter or Saturn, intense enough to be detected by a rocket, is also a distinct possibility. IMAGING TECHNIQUES Earth-based photography will continue to be a principal method of exploring planetary surfaces and atmospheres.
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From page 53... ...
It is possible that planetary images can be enhanced after they have been registered on photographic plates, perhaps after digitization or directly by an analogue technique. After-the-fact enhancement of detail in the Mariner IV television pictures of Mars and of the Surveyor pictures of lunar soil, and progress in restoring atmospherically degraded pictures of Earth satellites, indicate that postdetection processing may offer a promising means to improve ground-based photography in the next decade.
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From page 54... ...
A new method of scanning spectra has recently been used successfully: in a few seconds, the energy distribution over ranges of hundreds of angstroms is repeatedly measured and recorded by rocking the grating in such a way that its spectrum moves perpendicularly across the exit slit of the spectrograph. One of the advantages of the method is that it can be used when the atmospheric transparency is far less than what is generally regarded as "photometric." This is of particular importance in planetary observations involving transient phenomena and has the added advantage of effectively increasing telescope time for precise photometric photometry.
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From page 55... ...
RADAR, RADIO, AND OPTICAL FACILITIES Radar Since the first radar contact with a planet in 1961, six working groups in three countries (the United States, the Soviet Union, and the United Kingdom) have reported research in planetary radar astronomy.
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From page 56... ...
PLANETARY ASTRONOMY ClOUD ON -- MOININO UMl A344S APR 17, 1967 SCAN SLIT- ITS EXIT SLIT-20A APR 17, 1967 SCAN SLIT- 1"5 EXIT SLIT- 20A JUN 9, 1967 AP- 0:2 [« 10 IK OF AIC >j FIGURE 5 Scans of Mars near its 1967 opposition. The upper two curves are area scans made by Boyce in the E-W direction through Elysium.
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From page 57... ...
c .2 •-» u "O tt «, ^ a Q |- j 2 r 'E,'§ M S g 0O 00 i^ ITS ai .^ tn «ft en « K S C^ § § ||| O 8 8 1-4 rf| go fi c " E" S la e"'s 11 •o « "73 c ^3 ^ c li S 4-» O g *
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From page 58... ...
JB, Jodrell Bank, University of Manchester, England; JRO, Jicamarca Radar Observatory, Environmental Science Services Administration and Institute Geofisico del Peru, Jicamarca, Peru; MH, Millstone Hill, MIT Lincoln Laboratory, Westford, Mass.; USSR, Institute of Radio Engineering and Electronics, Crimea, USSR; DSCC, Deep Space Communication Complex, Jet Propulsion Laboratory, Goldstone Lake, Calif.; AIO, Arecibo Ionospheric Observatory, Cornell University, Arecibo, P.R.; HMF, Haystack Microwave Facility, MIT Lincoln Laboratory, Tyngsboro, Mass. research, radio astronomy, and tracking and communicating with deep-space probes.
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From page 59... ...
OBSERVATIONAL TECHNIQUES AND FACILITIES 59 might be realized if funding and authorization were provided in the near future. The antenna is the element of a large radar system that normally costs the most and presses hardest at the frontiers of technology.
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From page 60... ...
C u o 1 oration I fr Deep Space tion Com Arecibo Ion servatory Northeast R tory Corp 1 60
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From page 61... ...
Both the value and the cost of radar research call for a more forthright recognition of its potential in planetary astronomy. Radio Radio observations have been used to study planetary surfaces either at low resolution, referring to the entire surface, or at high resolution to make more detailed studies.
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From page 62... ...
82-ft reflectors Fully steerable 440-ft reflector National Radio Astronomy Observatory Northeast Radio Observatory Corporation Arecibo, Puerto Rico Southwest U.S.A. Massachusetts Mercury and Mars similar to those made of the Moon.
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From page 63... ...
Another instrument placed at a similar site of superb seeing is badly needed to permit observations of all planets where maximum resolution is of utmost importance and for observations of Mars at its most favorable oppositions which occur when the planet is at large southern declinations.
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