Displaying INCA Energetic Neutral Atom (ENA) Images: The Skymap is the input image projected onto the sphere of the sky, using the azimuthal projection with the 'north pole' of the sky sphere being the vertical axis. This display is designed for the analysis of ENA images, produced when the INCA high voltage ion and electron rejection plates are powered. This display is typically Saturn or Titan centered, in which case the vertical axis is aligned parallel with the body north pole. Other frames keep the vertical axis in the projected image parallel with the spacecraft Z axis. Various objects may be chosen for wire - frame overlay representation in the image display.

Displaying INCA data in Ion Mode: This menu also produces a (selectable) display known as Thumbnail (type=Square), for with the INCA FOV is represented in instrument, rectangular coordinates (vertical is elevation, parallel with the INCA slit and collimator plates, and with the Spacecraft Z axis, horizontal is azimuth, perpendicular to the INCA slit and collimator plates). This display is the appropriate choice for displaying INCA ion measurements when the charged particle rejection plates are turned off. Using the on - board magnetic field vector (provided courtesy of the Cassini MAG Investigation) the contours of constant pitch angle may be used as overlays in the Thumbnail projections. When the spacecraft is rolling about its Z axis, the coordinates of the Thumbnail map are the spin based coordinates to represent what a spinning imager 'sees'.

Menu section names are on the left and the links next to them jump to the menu sections.

Image Time - DO NOT SELECT A LONG INTERVAL (e.g., days) or the website will stall!

• Enter the start and stop year, day of year and hours.
  • The closest image(s) in time to the selected time will be displayed.
  • Select "Multiple Pages: Off" to plot only the first image in the set (especially useful when initially choosing plot parameters) or "On" to plot all the images in the set. (Only the first 20 images will be plotted, the rest will appear as output file hyperlinks at the top of the window.).
  • The estimated number of images that will be created is displayed to the right of the time when selected. This information is intended to help you decide if you have picked too much data for the application to display. If you select to display more than 25 images, a warning window will appear. Please consider selecting less than 25 images or do the images in sets since too many will overwhelm the web server.
• Select Update Window button.
  • Click UPDATE to generate output images (but set all other parameters below first!)
  • To page from one day to the next, use the << or >> buttons.
  • To page across more than one day, edit the Amount (doys) field and use the << or >> buttons..

Image Type & Color Map:

• Select the Image Type. Select the Skymap for ENA images or the Square (Thumbnail) for Ion mode images.
• Select the Image Resolution.
  • Spatial produces Hydrogen - - H+ low, H+ high, (where low and high refer to TOF - therefore "low" is higher in energy than "high".
    • For Spatial H, "low" corresponds to 55keV to 90keV,
    • "high" corresponds to 24keV to 55keV) or
  • Oxygen -
    • Ox low (170keV - 230keV),
    • Ox high (90keV - 170 keV).
  • The H+ high and both Ox images are at 32 x 32 pixel resolution over the 90 (azimuth) by 120 (elevation) INCA FOV.
  • The H+ low are at 64 x 64 pixel resolution.
  • High Time Res. images do not discriminate between species, but are typically dominated by hydrogen.
    • These images are at 32 x 32 pixel resolution over the 90 (azimuth) by 120 (elevation) INCA FOV.
    • They are produced at 4 times higher cadence than the Spatial and mTOF images.
  • High mTOF Res. Images, 16 x 16 pixels covering the INCA FOV, are produced for both Hydrogen and Oxygen. They are each available at 8 energies for each species - for H, they are produced at
    • 5 - 13keV (TOF7 or "high"),
    • 13 - 24keV (TOF6),
    • 24 - 35keV (TOF5),
    • 35 - 55keV (TOF4),
    • 55 - 90keV (TOF3),
    • 90 - 149keV (TOF2),
    • 149 - 227keV (TOF1), and
    • 227 - 360keV (TOF0 or "low").
  • For oxygen the energies are
    • 46 - 68keV,
    • 68 - 90keV,
    • 90 - 129keV,
    • 129 - 168keV,
    • 168 - 231keV,
    • 231 - 332keV,
    • 332 - 589keV, and
    • 589 - 1000keV.
• Select the Image TOF and Species.
  • mTOF images have low - high (8 values)
  • Spatial and Time images have only low and high TOF.
• Select the units. Counts, integral flux or differential flux.
• Select the celestial body relative to which the spacecraft location coordinate values radius, latitude, local time, L value and SKR Longitude is calculated.
• Select the desired frame in which sc_pos, spin_axis, and boresight vector are going to be returned in. Can take the values:
  • Boresight - The primary (X) axis is the CASSINI_MIMI_INCA boresight axis and is labeled X. The secondary (Z) axis is the Z axis of the IAU_SATURN frame (Saturn north spin axis vector). The Y-axis completes the right - handed system.
  • Saturn - This frame is a dynamically defined frame, defined as follows: the primary axis is the CASSINI spacecraft - to - Saturn vector and is labeled X. The secondary Z axis is the Z axis of the IAU_SATURN frame. The Y-axis completes the right - handed system.
  • Titan - This frame is a dynamically defined frame, defined as follows: the primary axis is the CASSINI spacecraft - to - Titan vector and is labeled X. The secondary Z axis is the Z axis of the IAU_TITAN frame. The Y-axis completes the right - handed system.
  • Saturn SZS - The primary axis, labeled Z, is parallel to the Saturn spin axis. The Y-axis is defined as the cross product of this vector with the Saturn - Sun vector. The X-axis completes the right - handed system and is directed "towards" the Sun.
  • SKR - Projected - This frame is a Saturn centered frame, similar to XINCA_SATURN_CENTERED, as the primary axis is defined as the spacecraft - Saturn vector. However, instead of utilizing the Saturn - sun vector as the definition of the proper clock angle about the primary axis, this frame uses the SKR prime meridian. By SKR, we refer to the currently available source for this information (SLS3, SLS4 south, etc.).
• Select the number of images to sum or average (2 - >) and select the averaging or summing option. The default is 1, which means no summing or averaging.
• Select the STEP between the output averaged or summed images.
  
  • The default, 0, has the effect of stepping forward in time by the number of images chosen for the sum or average, so that each output image is independent and contiguous. Choosing values other than 0 forces that value to be used. For example, if you are averaging over 10 images, leaving STEP at 0 means each successive group of 10 input images will be averaged into a successive output image. Choosing 10 will have exactly the same effect.
  • However, choosing 1 will result in a "sliding boxcar" average, where 10 input images are averaged to form 1 output image, then the program moves forward by 1 image accumulation time and forms another 10 image average for the next output image. This second average will include nine of the images included in the first average, plus one additional image forward in time. This achieves a sort of morphed sequence of images with strong persistence from one image to the next in the sequence, suitable for creating movie image frames.
• Select values by which to scale the images.
  • Leaving the scaling at zero forces automatic color bar scaling for the images (middle of the menu), by species and TOF (which means each horizontal row (time axis) in the output matrix of images will be scaled to the same min and max;
  • scale all together (meaning all of the images in the output matrix will be scaled to the same color bar) or scale them individually (meaning each output matrix image will be individually scaled to the min/max of the color bar).
• Select the image smoothing Applies a boxcar smoothing function to the mapped image. The purpose is to smooth the visible image to aid the eye in interpreting the image as a 3D structure and not make the eye unconsciously map it to the sphere. CAUTION!!: Localized features broaden. Care has to be taken when interpreting.
• Smoothing Edge Detection Turns on edge detection during smoothing. This leaves the edges of the INCA FOV un - smoothed, usually desirable since the algorithm is otherwise smoothing meaningful values inside the FOV with zeros outside.
• Exclude Counts (not well tested):
  • Low - Select whether to exclude counts below a certain value
  • High - Select whether to exclude counts above a certain value
• Colormap:
  • Select color map
  • Select the background color of the plot, black or white.
  • Select the color map scaling function, logarithmic or linear. Linear turns on linear scaling. Log turns on logarithmic scaling.
  • (See SCALE, above) Select the color map minimum, which is the minimum scaling value. Max is the maximum scaling value.
• Select the output format.
  • The selections are png, jpg and PS (not well tested).
  • To save the images, click on the File label with the right mouse button and use Save Link Target, or click on the image with the right mouse button and use Save Image As
• Charge
  • Select Neutral mode to select images when the INCA high voltage ion and electron rejection plates are powered at a threshold to produce ENA images.
  • Select Ion mode to select images when the INCA high voltage ion and electron plates are below the threshold for ENA images.
• Select the Compton Getting Filter option on button
  • Compton Getting: Use H+ or He. When displaying a hydrogen image, select He if you think the channel is dominated by He.
  • Compton Getting: Use Inputs. We have three methods of calculating the Compton Getting filter using the inputs.
    • The first method uses wind speed (km/s) alone.
    • The second method uses the velocity vector X,Y,Z in km with a specific coordinate frame.
    • The third method uses the wind speed (km/s) and Azimuth and Elevation in degrees in the INCA specific coordinate frame.
  • Compton Getting: Gamma Compton-Getting gamma parameter. Usually close to 2.0 in the solar wind rest frame.
  • Compton Getting: Wind Speed (km/s) Convective speed of the plasma. Default value is 500 km/sec.
  • Compton Getting: Apply Mag Flag to indicate if we want to only use the component of the velocity that is perpendicular to the magnetic field. E cross B.
  • Compton Getting: Select Method.
    • The Sun option will assume that the solar wind flows from the sun.
    • Saturn is the other case.
  • Compton Getting: Vector & Azimuth & Elevation Frame.
    • If the Use Inputs equals Velocity Vector then multiple coordinate frames are available.
      • INCA_LL - The MIMI INCA azimuth and elevation frame. The CASSINI_MIMI_INCA boresight axis goes into the screen. The X axis on the screen is the azimuth and the Y axis of the screen is the elevation of the INCA instrument.
      • The second frame is the spacecraft coordinate frame.
      • The third frame, KRTP, is in spherical polar Saturn centered coordinates, when R is radial away from Saturn, P is azimuthal, and T is meridional.
    • If the Use Inputs equals wind speed (km/s) and Azimuth and Elevation, then only the INCA_LL frame is available.
  • Compton Getting: Velocity Vector X (km) If the Use Inputs equals Velocity Vector then enter the X axis in kilometers.
  • Compton Getting: Velocity Vector Y (km) If the Use Inputs equals Velocity Vector then enter the Y axis in kilometers.
  • Compton Getting: Velocity Vector Z (km) If the Use Inputs equals Velocity Vector then enter the Z axis in kilometers.
  • Compton Getting: Azimuth (deg) If the Use Inputs equals wind speed (km/s) and Azimuth and Elevation, then enter aximuth in degrees.
  • Compton Getting: Elevation (deg)) If the Use Inputs equals wind speed (km/s) and Azimuth and Elevation, then enter elevation in degrees
  
  Pitch Angle Contours
  • Select the Pitch Angle Contours on button. The individual contours can be individually selected.
  • Pitch Angle Tolerance The pitch angle tolerance in degrees default value is 30 degrees.
  • Pitch Angle Color The color of the pitch angle can be selected.
• Image Contour The image contour option draws a line contour on the image itself. Values below the min and above the maximum are ignored. Map Overlays
• Select the Latitude and Longitude which set the portion of the sky and location in the selected frame to be viewed.
• Axis Multiplier This is an adjustment to the size of the axis for the planets and moons. Depending on the view, you may need to adjust this up or down to get a good axis size.
• Image Grid and FOV The Image grid will plot a grid of the INCA FOV native coordinates (elevation/azimuth) over the image FOV. The FOV option will only plot a perimeter frame showing the image FOV over the image.
• Body Time Width The width is used when multiple body overlays are plotted. It will trigger the overlays to plot multiple times during the image accumulation time. Useful when the scene geometry is changing quickly over the time span of the average.
• Center This function plots a single point at the center of the body.
• Grid This function plots a lat/lon grid the size of the body radius at the position of the body. Not useful when far from the body.
• Limb This function plots the limb of the body
• Title This function plots the first 2 letters of the body name slightly offset from the body center.
• Terminator This function plot the terminator of the body.
• Axis Frame This option draws the X,Y,Z axis in one or more of the following frames:
  • SSO Saturn Solar Orbit. In this coordinate system, the Sun's position and the 90 - degree Sun angle is fixed. The Sun is always at the (0.0,0.0) position.
    • X-axis points from Saturn to Sun
    • Y-axis Z x X
    • Z-axis is the Saturn orbital velocity x X
  • SZS Saturn Equatorial System.
    • Z-axis is parallel with Saturn spin axis
    • Y-axis = Z-axis crossed with the Saturn to Sun Line
    • X-axis = Y x Z (sunward)
  • IAU Saturn Body Fixed frame based on IAU rotation model
    • X-axis is where the prime meridian crosses the equator
    • Y-axis Z x X
    • Z-axis the body rotation axis
  • Saturn Variable Kilometric Radiation Frame - South and North.
    Saturn appears to have a different rotational period for the northern and southern hemispheres, and the following two frames, SKR South and SKR North attempt to capture these rotating frames.

    Each frame has +Z as the spin axis of saturn (+Z in the IAU_SATURN frame, and also +Z in the SZS frame) and is offset from the IAU_SATURN frame by a rotation about the Z axis. But note that this rotational offset changes with time, and since it coveres such a long time period, it is not practical to describe the offset as a single polynomial. So we put the offset into a C-Kernel. These frame definitions are specified by the plasma wave team (RPWS) and are meant to characterize the variable rotoation rate of Saturn. These frames are only defined over a limited period of time.
    CASSINI_SKR_SLS4_SOUTH: 2004-256T00:00:00.000 - 2010-314T23:59:59.997
    CASSINI_SKR_SLS4_NORTH: 2006-095T00:00:00.004 - 2009-258T23:59:59.997
    SKR_SLS3: 2004-001T00:00:00.000 - 2007-222T23:59:59.999
    SKR_SLS2: 2004-001T00:00:00.000 - 2006-240T23:59:59.999
    

  • The Saturn Moon System (SZM) frame is a dynamically defined frame. whose
    • Z-axis is the Saturn spin axis.
    • Y-axis of this frame is chosen to be the cross product of the Saturn - ReferenceMoon vector and this Z-axis.
    • X-axis completes the right - handed frame.
• Exobase The Exobase rings can be tuned on by entering both a low and high limit and the number of exobase rings desired for the body.
• Rings Either all rings or just separate ones can be turned on.