The NASA IMAGE mission involved launching a spacecraft to make detailed measurements of Earth's magnetosphere. It relied heavily on Tcl/Tk for processing and display of data.
The software developed for the mission is publicly available at: [L1 ]

A number of general purpose utility functions were written in Tcl for use in data processing. See [L2 ].
Some of the functions:
TUarrayMath Utilities applicable to numerical arrays
TUbessenFN Compute Bessel Functions
TUdataCT Geophysical coordinate transformations.
TUdataFilter 1-D Data Filtering
TUdataGrid Place a set of data into a regular data grid (matrix)
TUdataLSq1D Generalized 1D Least Squares Fit
TUdataLSq2D 2D Least Squares Fit
TUdataLSq3D 3D Least Squares Fit
TUdataMxMn Maximum/Minimum locator for arrays of data.
TUdataNLinLSq Non-linear 2D Least Squares Fit to a Function
TUdataNoOctal Convert integer string to numerical value
TUdataRnd1 Random number generator.
TUdataStat Determine the average value and variance of a data array.
TUdataSwap Swaps two data values
TUdateConv Convert Year/Day to Year/Month/Day and vice-versa
TUfileSeek Reposition the file pointer in a file
TUgammaFn Compute Γ(x) or ln(Γ(x))
TUgridCut Returns intensities along a cut through a grid
TUgridFill1D Fill gaps in a 1D data grid
TUgridFill12D Fill gaps in a 2D data grid
TUgridFilter Filter a 2D data grid
TUgridGrow Add rows or columns to a filled 2D grid
TUgridInfo Obtain information about a grid
TUgridMath Set of math operations suitable for data grids.
TUgridNoise Grid noise removal algorithms.
TUgridPrint Dump a grid to an ASCII file.
TUgridReGrid Regrid a grid
TUgridRowCol Get or replace a row or column of data in a grid
TUgridTrim Trim unused rows or columns off a grid
TUintegTrap Perform numerical integration
TUlinearEq Solve N coupled linear equations
TUmatrixEig Find eigenvalues and eigenvectors of a symmetric matrix
TUmatrixInv Matrix inversion and linear equation solver
TUmatrixMath Perform matrix operations
TUmatrixRot Rotation transformation matrix builder
TUpolyExp1D Computes the result of a 1D polynomial expression
TUpolyExp2D Computes the result of a 2D polynomial expression
TUpolyExp3D Computes the result of a 3D polynomial expression
TUreadUDFrc Parse the UDFrc file
TUsolveCubic Computes the solutions to a cubic equation.
TUsolveQuadratic Computes the solutions to a quadratic equation.
TUtimeCmp Compare two times
TUtimeFmt Change time formats.
TUtimeJulian Compute a Julian time
TUvecMath A set of vector utilities
TUyearLeap Determines if a year is a leap year or not.