mlso instrument

Mk I K-Coronameter Instrument

kolinski — Wed, 30 Mar 2022 17:36:27 +0000

Mk I K-Coronameter Instrument kolinski Wed, 03/30/2022 - 11:36

Instrument Description

Figure 1. Scientist Dick Hansen works on the K-Coronameter at MLSO in 1967.

The first K-coronameter (later known as Mk I) was an internally occulted white light coronameter to record the polarization brightness (pB) of the Thomson scattered K-Corona continuum emission. The instrument is shown on the spar at the Mauna Loa Solar Observatory (MLSO) in Hawaii in Figure 1. A mechanical layout of the K-Coronameter is shown in Figure 2. The brightness of the polarized light was measured with a sensitive photoelectric polarimeter using electro-optic modulation of the light beam and a half-wave plate made of two quartz plates whose optical axes were crossed and had thicknesses that differed by half a wavelength for l = 500 nm. These rotated at half the speed of a 360 degree scan around the corona (i.e. 8 minutes). Following the aperture stop the beam was modulated using a quarter-wave plate that included a ‘Z-cut’ crystal of ammonium dihydrogen phosphate (ADP) and a polaroid. The retardation of the beam was proportional to the voltage applied to the crystal. The voltage frequency, and the modulation of the light, was 50 Hz. A cone with a small hole drilled along its axis isolated the region of the corona for scanning around the Sun. A complete coronal scan took 4 minutes. Measurements were acquired every 5 degrees around the Sun. The half-angle of the cone could be varied to scan the corona at different heights from 1.125 out to 2 solar radii (as measured from Sun center). An example of the region isolated by the cone is shown in Figure 3. A full description of the instrument is provided in Wlerick and Axtell(1957), Newkirk 1958, and Lee and Fullerton 1961.

Figure 2. Schematic Drawing of the High Altitude Observatory Mk I K-Coronameter.

Instrument Details

8 cm aperture
Internally ‘occulted’
Central wavelength: 520.0 nm (see Newkirk, Curtis and Watson IGY report 1958)
Bandpass: 140 nm
Spatial Sampling: 39 arcsec per ‘pixel’
Spatial Resolution = 78 arcseconds
Field-of-View: 1.125 to 2 solar radii
Focal length: 193 cm
Background Noise level ~10^-08 B/Bsun
Instrument polarization < 10^-03

Available Data

Figure 3. A sample Mk I K-Coronameter scan taken on August 9, 1957 superposed on a limb image taken in the Helium D3 line (587.6 nm). The arrow points to a white circle that indicates the size of the scanning aperture.

The K-Coronameter took daily scans of pB intensity at up to 3 heights in the corona (see figure 3). It did not take images of the corona. Daily scans at 1.5 solar radii are available as digitized synoptic maps in fits and gif format covering the later mission from June 1965 until September 1978. Hard copy daily scans early in the mission (September 1956 through November 1960) are available in pdf format.

Science Goals

Figure 4. K-Corona pB intensity falloff with distance from the Sun as observed by the Mk I K-Coronameter in June 1959. K-coronameter data are indicated by the dot and triangle data points. Plots are from Newkirk et al. 1959, Nature. See Newkirk 1959 paper for more information. The K-Coronameter was able to observe the K-Corona to heights as great as 2 solar radii [16 arcmin] above the solar limb.

The primary scientific goal for the K-Coronameter was to observe the brightness of the white light continuum corona, and derive the coronal electron density, out to greater heights above the solar limb than could be viewed using coronal emission lines (see Figure 4). Coronal emission line brightness falls off much more rapidly than white light continuum emission which limited emission line observations to about 1.3 solar radii. Furthermore, it had been recognized that the spatial distribution of the white light corona often differed from the emission corona. It was hoped that simultaneous measurements of the white light and emission line corona could lead to a better understanding of the structure of helmet streamers and determine the cause of recurrent magnetic storms at Earth.

Calibration Information

Calibration of the Mk I K-Coronameter is discussed in detail in a 1958 IGY report by Newkirk, Curtis and Watson. Calibration discussion includes the correction for the sky signal, primary and secondary scattering, correction techniques and polarization angle. A second report to the IGY Solar Activity Series in 1962 by Heynekamp contains a further discussion of K-Coronameter data reduction and data accuracy and uncertainties. A further correction to the absolute photometric calibration of the K-Coronameter is noted by Fisher and Sime (1984) based on the calibration of HAO standard opals by Elmore, Streete and Eddy 1970. Links to papers are available in reference section below.

Observing Sites

The first operational testing of the HAO Mk I K-Coronameter was performed in March 1956 at the Sommers-Bausch Observatory of the University of Colorado in Boulder. It was mounted on the 26-foot equatorial spar at Climax Observatory in Colorado (see Figure 5) and began continuous day-to-day operation in September 1956. There were periods where the instrument and/or spar were down for upgrades or repairs. Down periods early in the mission occurred during these intervals: Dec. 1958 to May 1959; Oct. 1960 to Sept. 1961; May 1962 to Sept 1962. Due to degrading coronal skies at the Climax site, the Mk I K-coronameter was moved to the new Mees facility on Haleakala on Maui Hawaii and first observations were acquired in September 1962. Due to rapid development at Haleakala and flying insects at the site, the K-Coronameter was moved again to a 10-ft. equatorial spar at the new Mauna Loa Solar Observatory on the island of Hawaii in early December 1965 and began acquiring data on December 10, 1965. Mk I was eventually replaced by the Mk III K-Coronameter which began operation in January 1980.

Figure 5. The three observing sites that housed the HAO Mk I K-Coronameter. Left: The K-Coronameter operated at the Climax Observatory in Colorado from 1956 to 1962; Center: In 1962 the K-Coronameter was moved to the newly built Mees Observatory on Haleakala on Maui, Hawaii; Right: In 1965 the K-Coronameter was moved to the newly built MLSO on the island of Hawaii.

References for Mk I

Elmore, D.F., J.L. Streete, J.A. Eddy, 1970, Calibration of Opal Glass Attenuators, High Altitude Observatory, National Center for Atmospheric Research Astro-Geophysical Memorandum No. 178

Fisher, R. and D.G. Sime, 1984, Solar Activity Cycle Variation of the K Corona, Astrophys. J., 285, pp 354-358

Heynekamp, Chr. E., 1962, Observations of the Solar Electron Corona Part II, January 1958 to November 1960, IGY World Data Center A, Solar Activity Report Series, #16, July 4, 1962

Lee, Robert H., and John G. Fullerton, 1961, K-Coronameter Observed the Sun’s Electron Corona, Electronics, Nov. 24, 1961, McGraw Hill Publishing

Newkirk, Gordon, Jr., 1958, Emission-Line Polarization in Prominences, Pub. Astron. Soc. Of the Pacific, 70, 413, pp 185-190

Newkirk, G., Jr., G.W. Curtis and K. Watson, 1958, Observations of the Solar Electron Corona September 1956 to January 1958, IGY World Data Center A, Solar Activity Report Series, #4, 15, August 1958

Newkirk, G.A., G.W. Curtis, D.K. Watson, R. Manning, J. Shelby, 1959, The Inner Solar Corona during June 1959, Nature, 184, pp. 1308-1309

Wlérick, Gérard and James Axtell, 1957, A New Instrument for Observing the Electron Corona, Astrophys. J., 126, pp. 253-258

Mk II Coronal Activity Monitor Instrument

kolinski — Wed, 30 Mar 2022 17:32:04 +0000

Mk II Coronal Activity Monitor Instrument kolinski Wed, 03/30/2022 - 11:32

Description

The second K-coronameter developed by the High Altitude Observatory was known as the Coronal Activity Monitor and was later known as Mk II. The design drew heavily from the Mk I K-coronameter. Like the Mk I, the Mk II was an internally occulted white light coronameter designed to record the polarization brightness (pB) of the Thomson scattered K-Corona continuum emission at various coronal heights between 1.125 and 2.0 solar radii. The brightness of the polarized light was measured with a sensitive photoelectric polarimeter using electro-optic modulation of the light beam and a half-wave plate made of two quartz plates whose optical axes were crossed. Following the aperture stop the beam was modulated using a quarter-wave plate and a polaroid. The retardation of the beam was proportional to the voltage applied to the crystal. A cone with a small hole drilled along its axis isolated the region of the corona for scanning around the Sun. The Mk II contained a Lyot stop, an aperture stop, a Lyot spot and a calibration plate. An image of the Mk II instrument is shown in Figure 1.

Figure 1. John Moore works on the Mk II Coronal Activity Monitor (telescope with the open panel) at the Mauna Loa Solar Observatory (MLSO) in 1970. The instrument on the MLSO spar below the Mk II is the Mk I K-Coronameter.

The Mk II had a larger aperture than the Mk I and took advantage of newer (1960s) photo-multiplier tubes that were more sensitive to red wavelengths where the sky brightness is lower, reducing background noise. The Mk II utilized an S-20 photo-multiplier tube centered at 620 nm. It was designed to scan more rapidly than the Mk I in order to detect rapid changes (a few minutes) in the solar corona to study solar transients, i.e. coronal mass ejections (CMEs). The Mk II was capable of continuous scanning around the Sun but unlike the Mk I, it was also capable of scanning back and forth over small regions of interest in the corona where solar activity was more likely to occur. When not in activity monitor mode, the Mk II scanned the entire corona at eight heights between 1.125 and 2 solar radii in height increments of 0.125 solar radii. It took 2 to 3 hours to acquire 360 degree scans at all 8 heights.

Additional information about the Mk I hardware and data scans relevant to the Mk II instrument can be found on the Mk I homepage.

Instrument Details

13 cm aperture
Internally ‘occulted’
Central wavelength: 620.0 nm
Bandpass: 20 nm
Spatial Sampling: 30 arcsec per ‘pixel’
Spatial Resolution = 60 arcseconds
Field-of-view: 1.125 to 2 solar radii
Focal length: 272 cm
Background Noise level 1. 10^-08 B/Bsun
Instrument polarization -03

Available Data

The Mk II Coronal Activity Monitor took scans of pB intensity. It did not take images of the corona. Daily scans at 1.5 solar radii are available as digitized synoptic maps in fits and gif format covering the later mission from May 1969 until September 1978.

Science Goals and CME Observations

The primary science goal for the Coronal Activity Monitor was to observe solar transients (i.e. CMEs) in the corona. The primary goal was met by a number of observations of rapid coronal brightenings, followed by depletions that is now known to be a common signature of CMEs. One such observation was reported by Hansen at al. 1971. Figure 2 is a composite of two figures from the Hansen 1971 paper. The image on the left shows 5 scans of coronal brightness at a height of 1.5 solar radii taken on August 11-12, 1970. The scan times are noted in Table 1. The figure on the right shows the Mk II pB intensity vs time superposed with the 80 MHz observations of a moving Type IV source from the Culgoora radioheliograph. The rapid coronal brightening followed by a depletion is most likely a CME and occurs at about the same time and location as the moving Type IV source, indicating the likely presence of a shock wave produced by a fast-moving CME. An X-ray flare was also observed around the same time as the coronal transient by the Solrad 9 instrument on Explorer 37. The flare began after 23 UT and peaked at 23:44 UT. This Mk II observation was published in July 1971, 5 months before the first ever CME images were recorded by the NRL OSO-7 coronagraph.

Figure 2. Left plot shows the Mk II pB of the east solar limb between 40 and 120 degrees position angle (PA) at a height of 1.5 solar radii. The time of each pB measurement is shown in Table 1. The figure on the right is a superposition of the pB intensities at 1.5 solar radii with a curve of the 80 MHz observations from the Culgoora radioheliograph vs. time. Peak radio emission occurred at the time of rapid coronal depletion and in the same location in the corona (~85 degrees PA). See Hansen et al. 1971 for details.

SCAN NUMBER	TIME OF OBSERVATION
1	Aug 11 18:08 to 18:15 UT
2	Aug 11 22:05 to 22:16 UT
3	Aug 11 23:30 UT
4	Aug 11 23:37 to 23:50 UT
5	Aug 12 01:04 to 01:28 UT

Table 1. Observation time of pB scans shown in left plot of Figure 2.

Observing Site

Figure 3. The Mauna Loa Solar Observatory (MLSO) in Hawaii in the mid-1960s. Continuous observations from Mk II began on May 26, 1969. It operated along with the Mk I K-Coronameter and an halpa imaging monitor until September 28, 1978. MLSO is located at 11,200 ft (3400 meters) on the northern flank of the active volcano of Mauna Loa.

The HAO Mk II Coronal Activity Monitor was installed on a 10-ft. equatorial spar at the Mauna Loa Solar Observatory in Hawaii (see Figure 3) in the spring of 1969. Continuous observations began on May 26, 1969. It operated along with the Mk I K-Coronameter and a halpa imaging monitor until September 28, 1978. Mk I and Mk II were replaced by the MK III K-Coronameter, which began operation in January 1980.

SMM Coronagraph/Polarimeter

kolinski — Wed, 30 Mar 2022 17:23:32 +0000

SMM Coronagraph/Polarimeter kolinski Wed, 03/30/2022 - 11:23

The Coronagraph/Polarimeter (C/P) aboard the SMM satellite was provided by HAO to study the relationship of the corona to the flare process. The C/P used an arrangement of multiple internal and external occulting discs to block out the direct light from the Sun's photosphere, thereby permitting the faint light of the Sun's outer corona to be recorded.

SMM Coronagraph.

DATA AND DATA PRODUCTS

Our SMM pages contains data access links, CME gallery and catalog, and coronal synoptic maps.

IMAGE QUADRANTS

The telescope produced an image of the corona with a square field of view extending from approximately 1.6 solar radii to 4.1 solar radii at the sides and out to just over 6.0 solar radii along the diagonals. A sector mirror directed the image of one "quadrant" of the corona to the vidicon detector, as shown below.

SMM stitched quadrant image

A full view of the corona (excluding the pylon shadow) could be obtained by rotating the sector mirror through four orthogonal quadrant positions. Images of each quadrant may be 'stitched' together via software, as shown to the right and below , to form a 4-quadrant composite image. In the normal spacecraft orientation, the south polar region of the Sun's corona was obscured by the shadow of a pylon which supports the occulting disk assembly. The intensity of coronal features within about 20 degrees of the center of this pylon shadow was greatly attenuated. To uncover the south polar regions of the corona, the spacecraft was rolled 90 degrees for a single orbit several times each week. This was done occasionally in 1980, and on a regular basis during the period 1984-1989.

SPATIAL RESOLUTION

Images were frequently taken at a high spatial resolution of ~6 arc seconds during March, 1980, and immediately following the repair in 1984. However, the normal mode of observation produced coronagraph images in low resolution mode, wherein the spatial resolution (pixel size) was ~12 arc seconds.

OPTICAL FILTERS

The instrument package contained several spectral filters to meet the mission objectives. Most of the coronagraph images were obtained through a wideband filter in the "green" portion of the visible spectrum (half-power bandpass 500 -> 535 nm). During 1980, images were occasionally obtained through a very narrow bandwidth interference filter (530.0 -> 530.6 nm) containing the forbidden emission line of Fe XIV. Two coronal mass ejections have been identified in this bandwidth in the 1980 data set and are noted in the SMM Coronal Mass Ejection Catalog. Prior to 1987, a limited number of images were also obtained through a narrow bandpass filter (654.3 -> 658.3 nm) centered on the H-Alpha emission line of neutral hydrogen.

Three polarizing filters (with polarization planes oriented at 60 degree angles) were used to analyze the polarization of the observed radiation, both on a daily basis for synoptic purposes, and (when activity warranted) intermittently several times per day.

DUTY CYCLE

The "duty cycle" for the detection of coronal mass ejections by this instrument during the 1980 operations was quantified by Hundhausen et al. (1984), and was based on the average speed of mass ejections through the telescope's field of view. A minimal observing cycle for the detection of most mass ejections required that at least one complete set of images in the four quadrants be obtained during each SMM orbit (~90 minutes). During the 1980 operations, a selected quadrant was often observed for a prolonged period following a flare alert. As a result, images of the other three quadrants were not obtained. The 1980 duty cycle for mass ejection detection was quite low; in fact, images of all four quadrants were obtained in only 28% of the orbits.

With the resumption of observations in June, 1984, a change of observing philosophy was instituted, and nominal operations included at least one complete set of images from three quadrants (north, east, west) during each orbit. The south quadrant was added to this nominal sequence in August, 1984. The instrument's duty cycle for all years following the 1984 repair was quite high, with complete coverage averaging 78% of the available orbits each year. (Annual values for the duty cycle have been published by MacQueen and St.Cyr, 1991.)

IMAGE QUALITY

The quality of the coronagraph images is typically compromised by the existence of 3 dark lines and a dark spot, all of which were caused by a electronics problems in the readout beam for the vidicon detector. In additon, there are several small, bright dots, which are caused by pinholes in the detector. Finally, there are 5 rows of small, dark registration (reseau) dots. All of the above "artifacts" appear at nearly constant positions, although the widths of the readout beam blemishes vary in size somewhat from one image to the next.

Following the 1984 repair, the instrument experienced sporadic periods of degraded image quality. The degraded images appear to have dark and bright horizontal streaks randomly placed throughout the image. This streaking problem appeared for periods ranging from a few minutes to several weeks, and the effects on the identification of features (such as mass ejections) ranged from minor to severe. The horizontal streaking was probably caused by an on-board electronics problem; however, no correlation with any operational or environmental parameter was ever discovered.

CALIBRATION

The calibration of SMM data is documented in this paper. The figures and cover page are in this directory.

The SMM instrumental stray light and vignetting functions are available in graphic form and software is available to reproduce these graphics.

The f-corona model (the scanned technote), used for SMM, was developed by Munro, R. and modified for the Skylab mission. Software is provided to reproduce this graphic.

REFERENCES

Hundhausen, A.J., C.B. Sawyer, L. House, R.M.E., Illing, and W.J. Wagner 1984, J Geophys Res 89 2639

MacQueen, R.M., A. Csoeke-Poeckh, E. Hildner, L.L. House, R. Reynolds, A. Stanger, H. TePoel, and W.J. Wagner, 1980 Solar Phys, 65, 91-107

MacQueen, R.M. and O.C. St.Cyr, 1991 Icarus, 90, 96-106

Woodgate, B.E. and S.P. Maran, 1986, Space Station Automation II, SPIE Conference Proc. 729, 202

SMM Data Use Policy

The use of SMM C/P images for public education efforts and non-commercial purposes is strongly encouraged and requires no expressed authorization. However, it is requested that any such use properly attributes the source of the images as: "Courtesy of HAO/SMM C/P project team & NASA. HAO is a division of the National Center for Atmospheric Research, which is supported by the National Science Foundation."

Acknowledgements

The Solar Maximum Mission Coronagraph/Polarimenter was designed & operated by the High Altitude Observatory, a division of the National Center for Atmospheric Research, and funded by the National Science Foundation. The SMM Coronagraph/Polarimeter instrument was built by Ball Aerospace Systems Division. The SMM Spacecraft was built by Goddard Space Flight Center, and the SMM project was funded & managed by the National Aeronautics & Space Administration.

Mk3 & Mk4 Coronameters

kolinski — Wed, 30 Mar 2022 17:16:55 +0000

Mk3 & Mk4 Coronameters kolinski Wed, 03/30/2022 - 11:16

Mk3 on the MLSO spar

The Mark-III instrument was the third generation white light K-coronameter instrument at MLSO, and it operated from 4 February, 1980 through 30 September, 1999.

The field of view of the Mark-III K-Coronameter (Mk3) was 1.122 to 2.44 solar radii (as measured from sun center). The sun's corona was scanned by a linear array detection system which is rotated in solar position angle about the center of the solar disk. It took about three minutes to acquire one coronal image.

The Mark-III K-Coronameter data are scaled such that 104.4 pixels corresponds to one solar radius. Spatial sampling is 10 arcseconds radially by 0.5 degrees in azimuth. All data are rotated so that solar north is oriented straight up; solar north is known to within three degrees. Daily averaged images and mass ejection images from the K-Coronameter have instrumental `vignetting' left in the data to offset the coronal radial density gradient, allowing for better viewing of the corona. Calibrated images in units of polarization brightness (pB) are available and may be requested via the E-mail address listed above.

The Mark-IV K-coronameter, was constructed by HAO in collaboration with Rhodes College (Memphis, Tennessee). It has been in operation since October, 1998 at MLSO.

The Mark-IV K-coronameter replaces its predecessor, the Mark-III and features a high speed liquid crystal polarization modulator, a low noise CCD line array detector, and an achromatic polarizing beam splitter to measure Stokes I, Q, and U. Mark-IV produces polarization brightness maps of the lower corona in white light (700 to 900nm) from about 1.14 to 2.86 solar radii at a 3-minute cadence. Its plate scale is 5.95"/pixel, with data accuracy of approximately %15 and a noise level of approximately 4x10-9 B/Bsun.

2012 transit of Venus showing its silhouette in solar corona.

The Mark-IV instrument is a significant improvement over its predecessor in the following ways: lower system noise due to an improved detector and associated electronics, better sky noise rejection due to improved polarization optics and faster polarization modulation rate, higher spatial resolution, and a wider field of view.

These improvements result in higher quality polarization-brightness images which may be taken over a greater range of sky conditions than was heretofore possible.

For additional information about the Mark-III K-Coronameter instrument, see Fisher et al. (1981).
For information about the Mark-III K-Coronameter calibration technique, see Elmore et al. (1996).
For information about the Mk4 K-Coronameter calibration technique, see Elmore et al. (199?).

Mk4 summary slide

For more information about Mk3/Mk4, see END OF AN ERA: THE MAUNA LOA K-CORONOMETER IS DECOMMISSIONED

PICS & Coronado H-alpha Imagers

kolinski — Wed, 30 Mar 2022 17:01:51 +0000

PICS & Coronado H-alpha Imagers kolinski Wed, 03/30/2022 - 11:01

PICS on the MLSO spar.

The first H-alpha [656.3 nm] telescope at MLSO was the Prominence Monitor (PMON), which went into operation on 4 February 1980. It acquired both disk and limb images on B/W 35mm film. On 20 February 1994, the Acme 35mm film camera was upgraded to a Kodak Megaplus [Model 1.6] CCD detector (1534x1030 pixels) with a sample size of 3 arcseconds, and the telescope was renamed the Digital Prominence Monitor (DPM).

Photosphere in PICS.

On 25 September 1997, the PICS instrument replaced the Digital Prominence Monitor at MLSO. It provides several improvements over the DPM instrument, including optics for polarization measurement (since removed), improved temperature control, a narrower bandpass filter for disk observations, and improved optics for limb observations. PICS takes images at 656.3 nm, with a FOV of 2.3 solar radii, a spatial resolution of 2.9"/pixel, and a nominal cadence of 3 minutes.

PICS was decommissioned on 23 Feb, 2010 to make room on the tracking spar for the Coronal Multi-channel Polarimeter (CoMP). In its place, a small Coronado SolarMax60 Halpha imager was installed. The Coronado has a full FOV out to 2.25 Rsun at low latitudes and 1.6 Rsun over the poles before cropping (for large EPLs, the full FOV can be provided). Its spacial resolution is 1.77 arcseconds per pixel, with a nominal cadence of 3 minutes (capable of obtaining an image per second).

Coronado and solar cycle summary slide.

PICS summary slide.

CHIP Helium-I Imager

kolinski — Wed, 30 Mar 2022 16:55:16 +0000

CHIP Helium-I Imager kolinski Wed, 03/30/2022 - 10:55

CHIP on the MLSO spar.

The Chromospheric Helium-I Imaging Photometer (CHIP) was installed at the Observatory in April 1996. CHIP is a differential device using properties of the Helium-I line at 1083 nm as an indicator of both chromospheric and coronal structures. CHIP records images of the sun at 1083 nm, as well as at a number of other nearby wavelengths (for calibration purposes). It is basically composed of a liquid crystal variable retarder (tuneable) Lyot filter connected to an IR CCD.

CHIP is unique compared with other Helium-I imagers, in that it obtains images every 3 minutes, the high cadence crucial to study the rapid evolution of CMEs. In addition, observations from CHIP should provide better understanding of coronal holes, coronal arcades, and the interaction between open and closed magnetic field structures. See animation of eruptive prominence as recorded by CHIP.

Seven line and continuum exposures are recorded within 2 seconds. The difference of line and one continuum exposures is computed every 3 minutes to produce one 1083 nm image.

The CHIP FOV is approximately 1.8 solar radii. The CCD pixel size is 2.29 arcseconds and the measured spatial resolution is ~8 arcseconds. For additional information on the tuneable filter see Kopp et al. (1996).

CHIP instrument summary slide.

Precise Solar Photometric Telescope (PSPT)

kolinski — Wed, 30 Mar 2022 16:40:38 +0000

Precise Solar Photometric Telescope (PSPT) kolinski Wed, 03/30/2022 - 10:40

PSPT on its spar at MLSO

The Precision Solar Photometric Telescope (PSPT) is the centerpiece of the National Science Foundation (NSF) Radiative Inputs from Sun to Earth (RISE) program whose aim is to measure and understand variability in the solar radiative output. The PSPT produces seeing-limited full-disk digital (2048x2048) images in the blue continuum ( 409.4nm, FWHM 0.3nm ), red continuum ( 607.1nm, FWHM 0.5nm ), CaII K ( 393.4nm, FWHM 0.3nm ), CaII K Narrow Band Wing (NBW) (393.6nm, FWHM 0.1nm), and CaII K Narrow Band Core (NBC) (393.4nm, FWHM 0.1nm), with an unprecedented 0.1% pixel-to-pixel relative photometric precision. The addition of two narrow band CaIIK filters allows imaging of the CaIIK core to wing ratio with nearly the same precision.

PSPT dome at MLSO

The National Solar Observatory (NSO) designed and built three PSPT units, a prototype which is currently in operation at the Osservatorio Astronomico di Roma (OAR), and two primaries for installation at NSO Sac Peak and Mauna Loa Solar Observatory (MLSO). Currently, the units at MLSO and OAR are operated daily, with the NSO Sac Peak unit set aside for debugging and spare parts.

PSPT Blue (409.4nm)

PSPT Red (607.1nm)

PSPT CaIIK (393.4nm)

PSPT SRPM Image

The Solar Radiation Physical Modeling (SRPM) image mask is based on a semi-empirical center-to-limb corrected thresholding scheme (Fontenla et al. 1999, ApJ 518, 480). The scheme employs the red continuum images to isolate sunspot umbral and penumbral pixels and the CaIIK images to separate the facular (bright plage), plage, active network, network, and quiet Sun components.

LINK: more information and DATA ARCHIVE

PSPT SCIENCE GOALS:

PSPT Instrument Requirement: High precision (0.1%) photometric accuracy; Full disk photometry
Instrument Goal: High precision (0.1%) photometric accuracy

PSPT filter

PSPT BASIC DESIGN:

15cm refractor
Simple optical design (minimize scattered light)
Active mirror (image stabilization to ~0.25 arc sec)
2048x248 detector (~1 arc sec pixels)
3 + 2 filters

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COronal Multi-channel Polarimeter

kolinski — Wed, 30 Mar 2022 16:34:31 +0000

COronal Multi-channel Polarimeter kolinski Wed, 03/30/2022 - 10:34

The CoMP instrument (see Tomczyk, et al. 2008) can observe the coronal magnetic field with a full FOV in the low corona (~1.03 to 1.5 Rsun), as well as obtain information about the plasma density and motion. Like Solar-C, CoMP records the intensity and the linear and circular polarization (Stokes I,Q,U,V) of the forbidden lines of Fe XIII at 1074.7 nm and also at 1079.8 nm. In addition to detecting the POS field direction and the LOS field strength, CoMP also measures the LOS plasma velocity from Doppler observations in the wings of the line intensity (Stokes I), and the POS density from the ratio of the lines at 1074.7 and 1079.8 nm.

CoMP on the spar

View of CoMP from outside the dome.

This figure shows coronal properties measured by the HAO/NCAR funded Coronal Multi-channel Polarimeter (CoMP) instrument obtained by Steve Tomczyk and co-workers in April of 2005 on the 20-cm aperture OneShot coronagraph at NSO's Sacramento Peak Observatory in New Mexico.

These observations have a spatial sampling of 4.5 arcseconds per pixel and required 30 minutes of integration time to acquire a measure of the LOS magnetic field strength. The LOS field strength measurements shown at lower right, are significantly worse than those shown in the Solar-C data due to the smaller coronagraph aperture (20 cm vs. 46 cm on Solar-C), shorter integration time and smaller pixel size. The inclusion of LOS velocity measurements, along with intensity and linear polarization reveal ubiquitous propagating 3-5 mHz fluctuations in the solar corona, which have been identified as being predominately Alfvénic (Tomczyk et al. 2007). This remarkable observation is possible due to the combined measurements of LOS velocity and linear polarization over a wide range of coronal heights, each recorded at a very high time cadence (29 seconds).

Phase travel-time analysis (Jefferies et al., 1994, 1997; Finsterle et al., 2004; McIntosh et al., 2004) was used to detect the Alfvén waves in CoMP LOS velocity observations. Furthermore, it was possible to estimate that the observed fluctuations fall far short of providing the primary source of energy needed to heat the corona (see Tomczyk et al., 2007 for a full discussion). The detection of Alfvén waves in the corona provides important insights on the processes responsible for coronal heating. We will build upon this result with more sophisticated observations of coronal waves from the large aperture COSMO coronagraph. COSMO observations will allow us to use coronal seismology to explore both the magnetic and plasma structure of the corona. Coronal seismology combined with observations of the coronal magnetic field will provide new and powerful tools for solving the outstanding questions in coronal physics.

A list of CoMP publications can be found in the CoMP ADS Library

CoMP summary slide

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COSMO K-Coronagraph

kolinski — Wed, 30 Mar 2022 16:24:15 +0000

COSMO K-Coronagraph kolinski Wed, 03/30/2022 - 10:24

K-Cor on the MLSO spar

Download: Overview of K-cor instrument, calibration and data products guide

Get K-Cor Data

The COronal Solar Magnetism Observatory (COSMO) K-coronagraph (K-Cor) is one of three proposed instruments in the COSMO facility suite. It is specifically designed to study the formation and dynamics of coronal mass ejections and the evolution of the density structure of the low corona. The K-Cor records the polarization brightness (pB) formed by Thomson scattering of photospheric light by coronal free electrons. The National Center for Atmospheric Research (NCAR), via the National Science Foundation (NSF), provided full funding for the COSMO K-Cor, which was deployed to the Mauna Loa Solar Observatory (MLSO) in Hawaii in September 2013, replacing the aging MLSO Mk4 K-coronameter.

K-Cor Basic Description

The COSMO K-Coronagraph design was driven by the science goals of understanding the formation of CMEs and the structure and evolution of the low corona. Basic features of the K-Cor design include:

K-Cor schematic

Internally occulted refractive coronagraph
Field-of-view (FOV): 1.05 to 3 solar radii
Aperture: 20 cm uncoated singlet objective lens
Focal Length: 2 m (f/10)
Pass band: ~720 to 750 nm
Out-of-band rejection
Lyot Stop
4-state polarization modulation
Dual beam polarization ; 2 cameras to simultaneously record polarization states
5.5 arcsec pixels
Nominal cadence: 15 seconds (can run faster in campaign mode

Science Goals and Instrument Requirements

The four primary science goals that determined the design of the COSMO K-Cor are:

Understand the formation of CMEs and their relation to other forms of solar activity.
Identify Earth-directed CMEs (halos) in real time.
Measure the radial brightness in coronal holes from 1.05 solar radii to at least 1.5 solar radii.
Determine the density distribution of the corona over solar cycle time scales.

K-Cor/AIA Composite

To meet the first science requirement, K-Cor has a FOV down to 1.05 solar radii and a time cadence of 15 seconds. FOV goals were derived from a variety of existing observations. Most CMEs observed with the MLSO Mk3 and Mk4 K-coronameters appeared to form below the apparent height of the occulter (1.15 solar radii) and had their largest acceleration occur at or below 3 solar radii. Instruments such as TRACE and the YOHKOH SXT had high time cadence observations of CMEs (13 to 40 sec) that provided insights into the rapid formation and evolution of CMEs and their relation to other forms of activity but these instruments were limited; TRACE by its 8.5 arcmin field-of-view (FOV) and Yohkoh SXT by its insensitivity to plasmas with temperatures below 2 million degrees. The COSMO K-Cor will provide the first routine white light observations into the first coronal scale height with a time cadence optimized to study the dynamics of CME formation.

The next two science requirements, observing halo CMEs and density profiles in coronal holes, require polarization brightness (pB) noise levels of a few x 10^-10 B/Bsun (where Bsun is the brightness of the solar disk). Identifying halo CMEs in real time provides valuable information on CME properties for space weather forecasts. Measuring the radial brightness in coronal holes, and their finer structures such as polar plumes, yields density information in open field regions that can be used to constrain models of energy deposition into the solar atmosphere that drives the solar wind.

The final science goal requires a robust instrument, with reliable calibration hardware that can be operated and maintained over decades time scales.

Reliable and accurate calibrated data greatly enhances the ability to meet all mission science goals.

A summary of K-Cor instrument requirements is given in Table 1.

Table 1 - K-Cor Instrument Requirements

QUANTITY	UNITS	REQUIREMENT	COMPARISON TO MK
Field-of-view (FOV)	Solar Diameter	3	2.8
FOV lower limit	Arcsec	50	120
Spatial Sampling	Arcsec	6	5 to 23 (increased with height)

For more information about K-Cor, please visit: A New Coronagraph for Mauna Loa.

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Upgraded COronal Multi-channel Polarimeter

kolinski — Wed, 30 Mar 2022 16:15:39 +0000

Upgraded COronal Multi-channel Polarimeter kolinski Wed, 03/30/2022 - 10:15

Figure 1. UCoMP on the MLSO spar.

Get UCoMP Data

The Upgraded Coronal Multi-channel Polarimeter (UCoMP) is a 20-cm aperture Lyot coronagraph with a Stokes polarimeter and a narrow-band electro-optically tuned birefringent filter. It can image the intensity, full Stokes polarization, Doppler shift and line width across coronal emission lines in the visible and near-IR. The UCoMP is an upgrade of the Coronal Multi-channel Polarimeter (CoMP) instrument (Tomczyk, Card, Darnell et al., 2008); see Table 1 for performance comparison. The expanded capabilities of UCoMP provide polarization measurements over a wide range of coronal temperatures and out to greater coronal heights to explore the magneto-thermal structure of the corona in coronal holes, ‘quiet’ corona and active regions. The evolution of CMEs from build-up to eruption can be explored and MHD wave observations can be viewed to much greater heights, and over a wide range of coronal conditions. The tunable filter allows UComp to combine the strengths of simultaneous 2-D imaging and high-resolution spectroscopy into a single instrument. UCoMP is located at the Mauna Loa Solar Observatory (MLSO) operated by HAO/NCAR. UCoMP was installed in the spring of 2021, began acquiring data May 26, 2021, and is currently completing commissioning.

Figure 2. UCoMP in final stages of assembly at HAO/NCAR in Boulder.

The UCoMP demonstrates the technology of a large aperture (50 mm) tunable birefringent filter based on Lithium Niobate crystals and is a pathfinder instrument for the Coronal Solar Magnetism Observatory (COSMO) (Tomczyk et al., 2016) large coronagragh (LC). The LC will observe full Stokes polarimetry (intensity, linear and circular polarization) over a comparable wavelength range but with an aperture of 1.5 meters. COSMO consists of the LC, a chromospheric magnetometer (ChroMag) and the white light K-coronagraph (K-Cor). For more information on COSMO science and capabilities please see: Tomczyk et al. 2016.

PROPERTY	CoMP	UCoMP
Field-of_View [Rsun]	1.05 to 1.3	1.03 to 1.95 (see figure 3)
Spectral Range [nm]	1074 to 1083	530 to 1083
Spatial Resolution [arcsec]	9 (4.5 arcsec/pixel)	6 (3 arcsec/pixel)

Table 1. CoMP vs. UCoMP

UCoMP Description

Internally occulted refractive coronagraph
Aperture: 20 cm uncoated singlet objective lens
Field-of-view (FOV): 1.03 to 1.56/1.95 Rsun (see Figure 3)
Spatial resolution: 6 arcsec (3 arcsec / pixel)
Spectral Lines observed: Shown in Table 2 and Figure 5.
Spectral Resolution: Set by the birefringence of the Lithium Niobate crystals in the birefringent filter (see Figure 4)

Figure 3. UCoMP intensity image at 1074.7 nm used to illustrate the FOV.

Figure 4. Plot of UCoMP spectral resolution vs. wavelength.

SPECTRAL LINE	WAVELENGTH [nm]	logT_eff
FeXIV [corona]	530.3	6.15 to 6.49
FeX [corona]	637.4	5.80 to 6.24
ArXI [corona]	691.8	6.04 to 6.52
FeXV [corona]	706.2	6.20 to 6.63
FeXi [corona]	789.4	5.92 to 6.30
FeXIII [corona]	1074.7	6.08 to 6.41
FeXIII [corona]	1079.8	6.08 to 6.41
HI [chromosphere]	656.3	4.01 to 4.29
HeI [chromosphere]	1083	4.01 to 4.57

Table 2. Spectral Lines Observed by UCoMP

Figure 5. A sample of five of the nine spectral lines acquired with UCoMP showing coronal structures at various temperatures. These images were recorded on Feb 5, 2022. The coronal images are taken at ~1 minute exposure and the HI (Halpha) image is taken at 80 msec exposure.

Examples of some UCoMP Level 1 and Level 2 data products are shown in Figure 6 for a single spectral line (FeXIII 1074 nm). These products are created for each spectral line observed. The image below shows Stokes I (Intensity), Stokes Q/I and U/I that correspond to the percent linear polarization horizontally and at 45 degrees, respectively, and the ratio of L/I where L is the linear polarization = sqrt (Q2 + U2). The rotation of the corona is visible as the blue to red variation in the line-of-sight (LOS) Doppler velocity. The line width includes the instrumental profile. The Azimuth of the magnetic field is measured CCW from horizontal and is subject to a 180-degree ambiguity. The Radial Azimuth of the magnetic field is the azimuth measured CCW from the local radial direction. Zero-degree Radial Azimuth corresponds to magnetic field pointing in the radial direction.

UCoMP Level 1 and Level 2 data products from the FeXIII emission line at 1074.7 nm.

Additional information about the UCoMP instrument and science objectives are available; please see: Tomczyk et al. 2021 and Landi et al. 2016.

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mlso instrument

Mk I K-Coronameter Instrument

Instrument Description

Instrument Details

Available Data

Science Goals

Calibration Information

Observing Sites

References for Mk I

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Mk II Coronal Activity Monitor Instrument

Description

Instrument Details

Available Data

Science Goals and CME Observations

Observing Site

Category

SMM Coronagraph/Polarimeter

DATA AND DATA PRODUCTS

IMAGE QUADRANTS

SPATIAL RESOLUTION

OPTICAL FILTERS

DUTY CYCLE

IMAGE QUALITY

CALIBRATION

REFERENCES

SMM Data Use Policy

Acknowledgements

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Mk3 & Mk4 Coronameters

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PICS & Coronado H-alpha Imagers

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CHIP Helium-I Imager

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Precise Solar Photometric Telescope (PSPT)

PSPT SCIENCE GOALS:

PSPT BASIC DESIGN:

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COronal Multi-channel Polarimeter

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COSMO K-Coronagraph

K-Cor Basic Description

Science Goals and Instrument Requirements

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Upgraded COronal Multi-channel Polarimeter

UCoMP Description

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