Editing Mariner 9 (section)

== Instruments and experiments ==

=== Ultraviolet Spectrometer (UVS) ===
The Ultraviolet [[Spectrometer]] (UVS) studied the composition and density of Mars' upper atmosphere, detecting hydrogen, oxygen, and ozone. It worked on a wavelength range of 110–340 nm with a spectral resolution of 2.5 nm.<ref>{{Cite web |title=Mariner 9 Ultraviolet Spectrometer - General Information |url=https://lasp.colorado.edu/mariner9/137-2/uvs-general-information/  |access-date=2025-02-27 |website=Mariner 9 |language=en-US}}</ref>

The instrument identified [[Hydrogen atom|atomic hydrogen]] and oxygen in the upper atmosphere; provided data on the escape rates of these elements, influencing Mars' atmospheric evolution and mapped ozone distribution, showing seasonal variations.

=== Infrared Interferometer Spectrometer (IRIS) ===
The Infrared [[Interferometry|Interferometer]] Spectrometer (IRIS) measured [[thermal radiation]] emitted by Mars to analyze atmospheric composition, surface temperature, and dust properties. It worked on a wavelength range of 6–50 μm with a spectral resolution of 2.4 cm<sup>-1</sup>.<ref>{{Cite web |title=Mariner 9 Infrared Interferometer Spectrometer - NASA Planetary Data System |url=https://arcnav.psi.edu/urn:nasa:pds:context:instrument:iris.mr9  |access-date=2025-02-27 |website=arcnav.psi.edu}}</ref>

The instrument confirmed the presence of [[Carbon dioxide|CO<sub>2</sub>]] as the dominant atmospheric gas; detected water vapor in the Martian atmosphere; measured surface and atmospheric temperatures and provided insights into dust storms' thermal properties.

=== Celestial Mechanics ===
The [[Celestial mechanics|Celestial Mechanics]] Experiment was not a separate instrument. It used radio tracking to determine Mars' gravitational field and refine its mass estimates. It was based on analysis of [[Doppler effect|Doppler shifts]] in the spacecraft's radio signals and measuring range and range rate to track Mariner 9's precise motion.<ref>{{Cite journal |last1=Lorell |first1=J. |last2=Born |first2=G. H. |last3=Christensen |first3=E. J. |last4=Jordan |first4=J. F. |last5=Laing |first5=P. A. |last6=Martin |first6=W. L. |last7=Sjogren |first7=W. L. |last8=Shapiro |first8=I. I. |last9=Reasenberg |first9=R. D. |last10=Slater |first10=G. L. |date=1972-01-21 |title=Mariner 9 Celestial Mechanics Experiment: Gravity Field and Pole Direction of Mars |url=https://www.science.org/doi/10.1126/science.175.4019.317  |journal=Science |volume=175 |issue=4019 |pages=317–320 |doi=10.1126/science.175.4019.317|pmid=17814540 |bibcode=1972Sci...175..317L }}</ref> 

The experiment improved the understanding of Mars' gravitational field, provided more accurate estimates of Mars' mass and shape and helped refine the planet's rotational parameters.

=== S-Band Occultation ===
The S-Band [[Occultation]] Experiment was not a separate instrument. It used Mariner 9's radio signal at 2.295 GHz ([[S band|S-band]]) passing through Mars' atmosphere to study its density, pressure, and temperature profiles.<ref name=":0">{{Cite book |url=https://ntrs.nasa.gov/api/citations/19730012128/downloads/19730012128.pdf  |title=Mariner Mars 1971 Project Final Report |date=April 1, 1973 |publisher=JET PROPULSION LABORATORY}}</ref> 

The experiment measured vertical profiles of temperature and pressure in the Martian atmosphere, detected variations in the ionosphere and confirmed the presence of CO<sub>2</sub> as the main atmospheric component.

=== Infrared Radiometer (IRR) ===
The Infrared [[Radiometer]] (IRR) measured surface and atmospheric temperatures using infrared radiation. It worked on a wavelength range of 10–12 μm with a field of view of 1.7° × 1.7°.<ref name=":0" /> 

The instrument provided surface temperature maps of Mars, monitored thermal properties of dust storms and identified temperature variations between day and night cycles.

=== Visual Imaging System ===
The Visual Imaging System captured high-resolution images of Mars' surface, weather patterns, and moons. In a lower orbit, half that of [[Mariner 6]] and [[Mariner 7]] flyby missions, and with a vastly improved imaging system, Mariner 9 achieved a resolution of {{convert|320|ft|m|order=flip}} per [[pixel]], whereas previous Martian probes had achieved only approximately {{convert|2600|ft|m|order=flip}} per pixel.<ref name="Pyle2012" /><ref>{{Cite book |last1=Saunders |url=https://ntrs.nasa.gov/api/citations/19760004316/downloads/19760004316.pdf |title=Technical Memorandum 33-723 - Guide to the Use of Mariner Images |last2=Mutch |last3=Jones |date=October 15, 1975 |publisher=Jet Propulsion Laboratory}}</ref> It used broadband filters of various wavelengths optimized for surface and atmospheric studies.<ref name=":0" /><ref>{{Cite web |title=Mariner 9 Imaging Science Subsystem - NASA Planetary Data System |url=https://arcnav.psi.edu/urn:nasa:pds:context:instrument:iss.mr9  |access-date=2025-02-27 |website=arcnav.psi.edu}}</ref> 

The instrument provided the first global mapping of Mars' surface; discovered volcanoes, valleys, and dried riverbeds, suggesting past water activity; captured dust storms covering the entire planet and mapped Phobos and Deimos, Mars' two moons.