SPA Functions

This appendix provides a general description of all of the available functions currently used by the SPA program and is followed by a detailed description of all functions.

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Function Description Type

ABS Computes absolute value every channel

AVERAGE Compute the average of a group of scans

BASELINE Subtract a polynomial baseline from a scan; calculate RMS noise

C1 Activates the C1 function constant block

C2 Activates the C2 function constant block

C3 Activates the C3 function constant block

C4 Activates the C4 function constant block

C5 Activates the C5 function constant block

CD Change subdirectory

CHANNEL Change the definition of the x coordinate axis to channels

CLEAN Restore eliminated channels in a spectrum by interpolation good channels

EDIT Displays and changes the value of a header or data variable

ELIMINATE Zap bad channels from a spectrum

EQUATORIAL Calculate the equatorial coordinate displacements from an origin

ERASE Erase data from a sub directory or scans within the current sub directory

EXP Computes exponential of every channel

FILES Associates communication files with physical devices

FIRST Extract data from first spectrometer within the filter bank configuration

FLSR Change the definition of the x coordinate axis to LSR frequency

FOLD Rectify a frequency switched spectrum

FOURTH Extract data from fourth spectrometer within the filter bank configuration

FPLOT Plot spectrum and overlay gaussian

FSKY Change the definition of the x coordinate axis to sky frequency

FSOURCE Change the definition of the x coordinate axis to LSR frequency

GALACTIC Calculate the galactic coordinate displacements from an origin

GAUSS Calculate a non-linear least squares Gaussian fit to a spectral line

GENERATE Resamples the data to the specified x interval and resolution

HEADER Print selected header values of a scan

HISTOGRAM Generate a histogram of the values of a header variable

INTEGRATE Average repetitions within data; calculate difference between ons and offs

INVERSE Computes reciprocal of every channel

L10 Computes logarithm base 10 of every channel

LINE Measure parameters for a spectral line

LIST Lists contents of the tape directory and all sub directories

LN Computes natural logarithm of every channel

LOG Print position and summary of data

LSB Recalculates frequencies and velocities to appropriate to lower sideband

MAP Display values of a header value as a function of two other header values

MASK Set a pixel or horn mask for functions on the present command line

MAX Calculate channel by channel maximum value between two scans

MD Make new subdirectory

MIN Calculate channel by channel miniumum value between two scans

MPLOT Plot spectral line of each pixel within a scan by position

PANGLE Calculate angle of polarization from I,Q,U scans

PDEGREE Calculate degree of polarization from I,Q,U scans

PEAK Locate the least squares two dimensional Gaussian peak

PERROR Calculate error in the degree of polarization

PLOT Plot a spectrum, one pixel at a time

PRINT Print values of header and/or data for a scan

RD Remove subdirectory

READ Read data from SPA format magnetic tape

REST Change the definition of the x coordinate axis to rest frequncy

RUN Generate run of header variable as function of another header variable

SCALE Scale Y values of argument using Y values in scaling scan

SECOND Extract data from second spectrometer within the filter bank configuration

SEQUENCE Change the scan number of a scan

SHOW Display spectra of a group of scans on the same plot

SIGNAL Change frequenct scale to signal band for frequency switched data

SINE Subtract a sine wave from the argument observation; calculate RMS noise

SMOOTH Applies a smoothing filter to the spectrum

SORT Rearrange the argument list by sorting of a header variable

SOURCE Rearrange the argument list by isolating scans within a specified distance

SV Display spectra of a group of scans in a spatial-velocity diagram

SYNTHETIC Print the current list of user defined synthetic functions

TAPE Function for mounting and handling of magnetic tapes

THIRD Extract data from third spectrometer within the filter bank configuration

TRANSFER Transfer data from one sub directory to another

UNSEQUENCE Reverses a previous sequencing operation

USB Recalculates frequencies and velocities to appropriate to upper sideband

VLSR Change the definition of the x coordinate axis to LSR velocity

VSUN Change the definition of the x coordinate axis to heliocentric velocity

WRITE Write data to SPA format magnetic tape

YHISTOGRAM Generate a histogram of the y values of a scan

++ Perform scalar or vector addition on a scan

-- Perform scalar or vector subtraction on a scan

** Perform scalar or vector multiplication on a scan

** Perform scalar or vector exponentiation on a scan

// Perform scalar or vector division on a scan

}

NAME

AVERAGE

PURPOSE

Compute the average of a group of scans

SYNTAX

scan1 scan2 scan3 ... scan(n) AVE[RAGE]

TYPE

n 1

COMMENTS

Average calculates a pixel by pixel average of a group of scans. There is no shifting to align the observations in velocity space. If the observations an equal number of pixels can be averaged. Uncleaned eliminated channels are not averaged into the final scan. The header of the first argument is updated and becomes the header of the resultant scan. To update the rms values within the resultant scan, one must rerun the BASELINE function.

FUNCTION CONSTANTS

WEIGHTING 1 - weight the observations equally. 2 - weight proportional to the inverse square of the RMS noise (YSIGMA) measured during previous use of the BASELINE or SINE functions. 3 - weight proportional to the integration time.

EXAMPLE

To average all scans within the sub directory S14, S14 AVERAGE Pixel 4 of scan 4500 contained too many bad channels to be useful. The footprint was later reobserved with good data in all pixels as scan 5000. To average all of the good data and dispose of the bad data in pixel 4 of scan 4500, set the MASK function constants number of pixels to mask to -1, MASK TYPE to 1 and pixel 4 as the pixel ID to mask. Then type: 5000 4500 MASK AVERAGE It is necessary to place scan 5000 as the first argument since it contains the good data for pixel 4.

HEADER CHANGES

TINT, QTINT

NAME

BASELINE

PURPOSE

Subtract a polynomial baseline from a scan and calculate RMS noise.

SYNTAX

scan BAS[ELINE]

TYPE

1 1

COMMENTS

Coefficients of a Chebychev polynomial are determined from a least squares fit to the observational data within the specified intervals. After the fitted baseline has been subtracted, the rms noise level is calculated for data within the specified intervals and stored in the header YSIGMA, for each pixel.

FUNCTION CONSTANTS

EXAMPLE

To subtract a baseline from scan 6756, 6756 BASELINE

HEADER CHANGES

YSIGMA, QYSIG

NAME

CD

PURPOSE

Change to another subdirectory.

SYNTAX

CD SUBDIR

TYPE

1 1

COMMENTS

The S file is composed of subdirectories in which one can write data. In order to reference data by a scan number within a given subdirectory, the active subdirectory must be equal to the desired subdirectory. The CD command allows one to change the active subdirectory.

EXAMPLE

In order to accessa nd plot scan 9564 within the T file, the user must first change to the T file and then reference the scan by number cd T 9564 PLOT

NAME

CHANNEL

PURPOSE

Change the x coordinate axis to channels of the spectrometer.

SYNTAX

scan CHANNEL

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed according to values stored in the scan header. These changes are reversible at any time.

HEADER CHANGES

KX

NAME

CLEAN

PURPOSE

Restore eliminated channels in a spectrum by interpolating between the nearest good channels.

SYNTAX

scan CLE[AN]

TYPE

1 1

COMMENTS

Channels within a spectrum which had been zapped by the previous use of the ELIMINATE function or originally set to a value greater than 10 by the nearest good channels.

EXAMPLE

To interpolate over any bad channels removed by the ELIMINATE function in scan 7088 ELIMINATE CLEAN

NAME

C1, C2, C3, C4, C5

PURPOSE

Specifies which of the five function constant blocks should be active.

SYNTAX

C1

TYPE

1 1

COMMENTS

The SPA functions are characterized by function constants. Since the user may wish to vary the values associated with these constants, the SPA program provides five separate versions of the complete function constant list. When a new block is requested, the previous block is stored on disk

EXAMPLE

To calculate and print the line parameters of two velocity components within a spectrum stored in scan 6002 set the integration range for each component within function blocks C1 and C2 respectively and type, 6002 C1 LINE PRINT C2 LINE PRINT The users is left with function constants stored in C2.

NAME

EDIT

PURPOSE

Displays and changes the value of a header or data variable.

SYNTAX

scan EDI[T]

TYPE

1 1

COMMENTS

There are two modes of operation of the EDIT function. If -10 < VALUE < 10 , then the header variable is automatically assigned this value. If VALUE=-10 , then the present value of the variable is output. After viewing its present value, the user can enter a new value. If no value is entered, the variable retains its old value. If VALUE is not equal to 10 , the header value is automatically given this value. For multi pixel scans, the function is not looped through all of the pixels since most headers apply to all pixels.

FUNCTION CONSTANTS

VARIABLE NAME specifies the name of the header variable The recognized name are the first four letters of any variable within the scan header given in Appendix D

VALUE new value of variable or D for interactive entry of new value for each argument

NAME

ELIMINATE

PURPOSE

Remove bad channels from a spectrum.

SYNTAX

scan ELI[MINATE]

TYPE

1 1

COMMENTS

There are three operation modes in order to mask bad channels. Channels are eliminated within an interval by

1. median filter,
2. as the most extreme value from the median
3. unconditionally if only 1 channel is specified within a range.

The median and standard deviation are calculated exclusive of the minimum and maximum values within each interval.

FUNCTION CONSTANTS

TOLERANCE if > 0, number of standard deviations from the median from which channels are eliminated < 0, number of the most extreme channels to eliminate. XL1 XU1 XL2 XU2 XL3 XU3

EXAMPLE

To eliminate all channels in scan 5001 which deviate by more than 3 from the median value within the specified intervals, set TOL=3.0 and type, 5001 ELIMINATE To elimate the two most extreme channels within each interval of scan 7500, regardless of sign, set TOL=-2.0 and type, 7500 ELIMINATE

NAME

EQUATORIAL

PURPOSE

Recalculate the equatorial coordinate displacements (DALP, DDEC) from an equatorial coordinate origin.

SYNTAX

scan EQU[TORIAL]

TYPE

1 1

COMMENTS

Displacements along the equatorial coordinates are calculated with respect to a new origin. This is useful if two maps were made of the same region but with different center positions. This function also calculates the distance from th center.

FUNCTION CONSTANTS

RA0 Right Ascension (HHMMSS.S) of the coordinate origin.

DEC0 Declination (DDDMMSS.S) of the coordinate origin.

EXAMPLE

A map was observed on two days with a different center reference position so the offsets within the header are not on the same grid. All of the data is in the sub directory S8. To place these positions on one grid and the store the result in the same location, set RA0 and DEC0,

HEADER CHANGES

DALP, DDEC, RACEN, DECCEN, DIST, DX, DY

NAME

ERASE

PURPOSE

Erase data from a sub directory or scans within the current sub directory.

SYNTAX

scan ERA[SE]

TYPE

0 0

COMMENTS

Remove scans within a sub directory to free locations for other uses. If scan numbers are used to identify which data are to be removed, then only those scans within the current sub directory are erased. Entire sub directories can be also be erased.

EXAMPLE

To remove scans 4005 thru 4050 within the current sub directory, 4005 to 4050 ERASE To erase the contents within sub directories S4, S5, and S6, S4 S5 S6 ERASE

NAME

FILES

PURPOSE

Associates communication files with physical devices

SYNTAX

FIL[ES]

TYPE

1 0

COMMENTS

Printed output can be redirected to the screen, printer, plotter or disk file. In most cases, the user will wish to have command input, command responses, printing and plotting directed to the user screen user screen (A). For some functions, the execution is limited by printed output to the screen. To speed up this processing, one can direct the output to the NULL device (NO). In addition, once can direct printed output to a file, logical unit 10 (DI). For tape I/O operations, the tape file and tape read mode are set with the FILES function.

FUNCTION CONSTANTS

COMMAND INPUT device where commands are input

COMMAND RESPONSES device where program responds to commands or writes error messages

PRINTER device for printer output

PLOTTER device for plotting

TAPE current tape file

TAPE READ MODE sequential or scan mode

NAME

FIRST

PURPOSE

Extract data from the first spectrometer within a multi- spectrometer configuration.

SYNTAX

scan FIR[ST]

TYPE

1 1

COMMENTS

For data taken with several backends, these functions extract data taken within the respective spectrometer within the observed configuration. Once a spectrometer has been selected, it is not possible to extract data of the other spectrometers except by recalling the original data.

EXAMPLE

To extract data from the Q23 spectrometer in the observed configuration (Q23 Q15 QEF) of scan 7812, type: 7812 FIRST

HEADER CHANGES

NIN, IN1, KBE, LENSCAN, XCH1, XVEL1, XFR1, DCHDIN, DVELDIN, DFRDIN

NAME

FLSR

PURPOSE

Change the x coordinate axis to frequency with respect to the local standard of rest.

SYNTAX

scan FLSR

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed to frequency with respect to the local standard of rest. This change is reversible at any time.

HEADER CHANGES

KX, XFR1, DFRDIN

NAME

FOLD

PURPOSE

Rectify a frequency switched spectrum

SYNTAX

scan FOL[D]

TYPE

1 1

COMMENTS

For channels within a frequency switched spectrum which are looking at the same X coordinate, the line in the reference is subtracted from that in the signal and or the line in the signal is added to that in the reference.

FUNCTION CONSTANTS

FOLD = 0 - subtract reference from signal = 1 - add signal to reference = 2 - do both of the above

EXAMPLE

To rectify the data in the first spectrometer of frequency switched spectrum in scan 7000 7000 FIRST FOLD

NAME

FOURTH

PURPOSE

Extract data from a spectrometer within a multi configuration of spectrometers.

SYNTAX

scan FOU[RTH]

TYPE

1 1

COMMENTS

For data taken with several backends, these functions extract data taken within the respective spectrometer within the observed configuration. Once a spectrometer has been selected, it is not possible to extract data of the other spectrometers except by recalling the original data.

EXAMPLE

To extract data from the F4 spectrometer in the observed configuration (F2 F3 F1 F5 F4) of scan 7812, type: 7812 FOURTH

HEADER CHANGES

NIN, IN1, KBE, LENSCAN, XCH1, XVEL1, XFR1, DCHDIN, DVELDIN, DFRDIN

NAME

FPLOT

PURPOSE

Plot a spectrum and overlay gaussian generated from header variables YMAX, XMEAN, XWIDTH

SYNTAX

scan FPLO[T]

TYPE

1 1

COMMENTS

FPLOT displays the data within a scan in histogram mode and overlays a gaussian generated from the header variables YMAX, XMEAN, and XWIDTH in solid line mode. These header variables are defined by the functions LINE and GAUSS. Note that if multiple gaussians are fit to the profile, only one component is plotted.

FUNCTION CONSTANTS

EXAMPLE

To graphically view the the gaussian fit of a spectrum in scan 7001 type: 7001 GAUSS FPLOT

NAME

FSKY

PURPOSE

Change the x coordinate axis to sky frequency.

SYNTAX

scan FSKY

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed to frequency with respect to the sky. This change is reversible at any time.

HEADER CHANGES

KX, XFR1, DFRDIN

NAME

FSOURCE

PURPOSE

Change the frequency scale to rest frame of the source.

SYNTAX

scan FSOURCE

TYPE

1 1

COMMENTS

The frequency scale of a scan is changed to the rest frame of the These changes are reversible at any time.

HEADER CHANGES

KX, XFR1, DFRDIN

NAME

GALACTIC

PURPOSE

Recalculate the galactic coordinate displacements (DL, DB) from an galactic coordinate origin.

SYNTAX

scan GAL[ACTIC]

TYPE

1 1

COMMENTS

Displacements along the galactic coordinates are calculated with respect to a new origin. This is useful if two maps were made of the same region but with different center positions. This function also calculates the distance from the center. For multipixel scans, the data must have been taken in galactic coordinates (see DEWMODE).

FUNCTION CONSTANTS

L0 longitude (DDD.DDD) of the coordinate origin.

B0 latitude (DDD.DDD) of the coordinate origin.

HEADER CHANGES

DL, DB, LCEN, BCEN, DX, DY

NAME

GAUSS

PURPOSE

Calculates a non-linear least squares Gaussian fit to a spectral line within a specified x interval.

SYNTAX

scan GAU[SS]

TYPE

1 1

COMMENTS

A non-linear Gaussian fit of up to 5 peaks of a spectral line is calculated using the CURFIT routine in Bevington (p. 237). If only one peak is specified, then the resultant fit paramters and uncertainties are automatically updated into the header variables YMAX, YINT, YTERR, XMEAN, XMERR, XWIDTH, XWERR, and XSIGMA. If more than one peak is to be fit, then the user is prompted for which peak's parameters are to be stored in the header.

FUNCTION CONSTANTS

NPEAKS the number of peaks to fit to the spectral line

EXAMPLE

To calculate a gaussian fit to scan 6756, type: 6756 GAUSS

HEADER CHANGES

YMAX, XMEAN, XMAX, XWIDTH, YINT, YSIGMA, XMERR, XWERR, QYMAX, QYSIGMA, QXWIDTH, QYINT, QYTERR, QXMERR, QXWERR

NAME

GENERATE

PURPOSE

Resamples the data to the specified x interval and resolution

SYNTAX

scan GEN[ERATE]

TYPE

1 1

COMMENTS

The data is shifted and linearly interpolated to produce a new spectrum with a given channel spacing over the specified x coordinate range. This function is useful for aligning data in X in preparation to averaging or making a spatial velocity map.

FUNCTION CONSTANTS

DX desired change in channel, frequency, or velocity with index in data (1.0) XLOWER XUPPER

EXAMPLE

To rebin a spectrum 13001 with velocity resolution 0.65 km/sec to a coarser resolution of 1.0 km/sec to gain better signal to noise

HEADER CHANGES

NAME

HEADER

PURPOSE

Print selected header values of a scan.

SYNTAX

scan HEA[DER]

TYPE

1 1

COMMENTS

Up to eight header values selected by the user are displayed on the printer. If the number of header values is > 0, then a descriptive heading is also given. If the number of variables is set to 9, then the specified range of Y data is also listed.

FUNCTION CONSTANTS

NHEADERS number of headers to print

EXAMPLE

To list the header values DALP, DDEC, YMAX, YSIGMA, XMEAN, and XMERR of scan 11001 11001 HEADER

NAME

HISTOGRAM

PURPOSE

Generate a histogram of the values of a specified header variable for a group of scans.

SYNTAX

scan1 scan2 scan3 ... scan(n) HIS[TOGRAM]

TYPE

n 1

COMMENTS

A histogram is generated from the header value of a group of scans and placed in the X register.

FUNCTION CONSTANTS

HEADER VARIABLE variable to histogram

XLOWER lower limit of header values to be

XUPPER upper limit of header values to be DX

EXAMPLE

To see the distribution of the header value YINT of all scans in S1, type: S1 HISTOGRAM PLOT

HEADER CHANGES

NIN, IN1, KX, NHORN, LENSCAN, XCH1, DCHDIN

NAME

INTEGRATE

PURPOSE

Average repetitions within the data and calculate difference between off and on intensity.

SYNTAX

scan INT[EGRATE]

TYPE

1 1

COMMENTS

Average the repetitions which occur within the Y array as a result of position switching continuum observations. The difference between the averaged on position samples and averaged off position samples is stored in the header variable YMAX. The rms noise calculated from the off position data is stored in YSIGMA. These results can be displayed with the PRINT function with digit=5.

HEADER CHANGES

NIN, YMAX, YSIGMA

NAME

LINE

PURPOSE

Measure parameters for a spectral line within the specified x interval.

SYNTAX

scan LIN[E]

TYPE

1 1

COMMENTS

The spectral line is characterized by a maximum value, integrated intensity and distribution moments within the x coordinate limits. If YSIGMA has been calculated from a previous use of the BASELINE function, then statistical errors are determined for the header values YINT, XMEAN, and XWIDTH. These are stored in the real*4 header values YTERR, XMERR and XWERR respectively.

FUNCTION CONSTANTS

HEADER CHANGES

YMAX, XMEAN, XMAX, XWIDTH, YINT, YTERR, XMERR, XWERR, QYMAX, QXWIDTH, QYINT, QYTERR, QXMERR, QXWERR

NAME

LIST

PURPOSE

Lists contents of the tape directory and all disk subdirectories

SYNTAX

LIST

TYPE

1 1

COMMENTS

The user is prompted to display the contents of the entire magnetic tape directory or just the current tape directory (MT01, MT02, ...) and the contents of the entire S file directory or just the current sub directory (S1, S2, ...).

FUNCTION CONSTANTS

TAPE FILE LIST FORMAT 0=none, 1=short, 2=long

S FILE LIST FORMAT 0=none, 1=short, 2=long

NAME

LOG

PURPOSE

Print position and summary of data for a group of scans in the form of an observing log.

SYNTAX

scan1 scan2 scan3 ... scan(n) LOG

TYPE

n n

COMMENTS

Information for a group of scans is displayed on the printer device. There is only one entry per scan.

EXAMPLE

To generate a log of all scans in the S7 sub directory, type: S7 LOG

NAME

LSB

PURPOSE

Recalculate frequencies and velocities for lower sideband.

SYNTAX

scan LSB

TYPE

1 1

COMMENTS

Frequencies and velocities are calculated for lower sideband. These changes are reversible at any time.

HEADER CHANGES

XVEL1, DVELDIN, XFR1, DFRDIN, KLO

NAME

MAP

PURPOSE

Display values of a header value for a group of scans as a function of two other header values (normally positional headers such as dalp,ddec).

SYNTAX

scan1 scan2 scan3 ... scan(n) MAP

TYPE

n n

COMMENTS

Values of a scan header are displayed in either numeric or contour representations. In normal use, the x and y axes represent positional headers such as dalp,ddec or l, b to generate a map. If a contour display is requested, the user is prompted for the type of grid - regular or irregular. An irregular contour map requires extensive interpolations and therefore, is slow. This option is limited to 300 pixels. A regular contour map simply indexes data into an array. It is limited to 8192 pixels. For both contour and shading representations, the user is prompted for lower and upper values for the contour range. If these are equal, the user is prompted for actual contour levels.

FUNCTION CONSTANTS

X VARIABLE name of header variable to be used as x coordinate.

Y VARIABLE name of header variable to be used as y coordinate.

Z VARIABLE name of header variable to be used as z coordinate. LEFT RIGHT BOTTOM TOP

CONTROL ten coded digits controlling physical parameters of the plot (0422851530).

CONTROL digit description

1 = 0 - no grid lines drawn across center of plot = 1 - grid lines drawn across center of plot

2 = 1 - z values printed on graph = 2 - points = 3 - lines connecting points = 4 - labelled contours = 5 - unlabelled contours = 6 - dense shading = 7 - optimum density shading = 8 - less dense shading = 9 - lowest density shading

3 4010 x coordinate of lower left corner of grid in units of 100

4 4010 y coordinate of lower left corner of grid in units of 100

5 x length of graph in 4010 coordinates in units of 100

6 y length of graph in 4010 coordinates in units of 100

7,8 size of numbers along x and y axes

9,10 size of labels

EXAMPLE

To display a map of header values of all scans in S1, type: S1 MAP To display a map of header values of pixel 8 only, set the mask and type: S1 MASK MAP

NAME

MASK

PURPOSE

Set a pixel or horn mask for functions on the present command line.

SYNTAX

scan MAS[K] other functions

TYPE

COMMENTS

For multi pixel data, all pixels within a scan are processed by default for each command line. MASK is used in order to process only selected pixels within a scan for a given command line. The mask is only active for those functions following the MASK function. MASK TYPE allows the user to set the mask according to the pixel ID or horn ID. NMASK sets the number of pixels (horns) to mask. The user is prompted for the ID of each pixel (horn). For NMASK > 0, only those pixels (horns) are processed. For NMASK < 0, all pixels (horns) except those listed are processed. Regardless of whether a pixel is processed or not, the data for each pixel remains within the scan.

FUNCTION CONSTANTS

MASK TYPE 1 - mask is set by pixel 2 - mask is set by horn

NMASK number of pixels (horns) to mask

EXAMPLE

To eliminate a bad channel in pixel 4 of scan 4500 and then display the result, type: 4500 MASK ELIMINATE PLOT

NAME

MD

PURPOSE

Creates a new subdirectory within the S file.

SYNTAX

MD SUBDIR

TYPE

1 1

COMMENTS

When initialized, the S file contains 16 subdirectories, labelled S1, S2, ... S16. A user can dynamically create additional subdirectories with any 3 character label which does not conflict with function names, synthetic definitions, or other subdirectories. There is a limit of 90 subdirectories allowed within a given S file.

EXAMPLE

To create a subdirectory labeled MHH MD MHH

NAME

L10, LN, EXP, ABS, INVERSE

PURPOSE

Computes function of every channel.

SYNTAX

scan L10

TYPE

1 1

COMMENTS

Simple arithmetic operations are calculated for each channel within a scan. L10 calculates the log base 10 of every channel. LN calculates the natural log of every channel. EXP computes the exponential of every channel. ABS determines the absolute value of every channel. INVERSE computes the reciprocal of every channel.

EXAMPLE

To calculate the exponential of every channel in scan 5689, plot the result and place in the subdirectory s16 S16 = 5689 EXP PLOT

NAME

+, -, *, /, **, MIN, MAX

PURPOSE

Perform scalar or vector arithmetic on a scan.

SYNTAX

scan1 + scan2 + scan3

TYPE

2 1

COMMENTS

Arithmetic operations on a scan or between two scans are issued on the command line. If the second argument contains a decimal point, then the arithmetic is scalar. If the argument is an integer (no decimal point), it is treated as a scan number and the arithmetic is vectorial. The order of the arithmetic on a command line follows the standard precedences.

EXAMPLE

To add scans 6001 6002 6003, divide the result by 2.5 and place in s10, S10 = ( 6001 + 6002 + 6003 ) / 2.5

NAME

MPLOT

PURPOSE

Plot spectral line of each pixel within a scan by position

SYNTAX

scan MPL[OT]

TYPE

1 1

COMMENTS

Data taken with a multiple array receiver are stored as 15 or 30 pixel scans according to the data observing mode. MPLOT allows one to view all of the data within a scan on a single plot. The scan number is printed at the top of the plot and the horn used to observe the pixel is printed within each box.

FUNCTION CONSTANTS

CONTROL ten coded digits controlling physical parameters of the plot (0422851530).

EXAMPLE

To display all of the spectra within scan 6096, type: 6096 MPLOT

NAME

PANGLE

PURPOSE

Calculate polarization angle from three scans containing Stokes paramters I,Q, and U.

SYNTAX

scan1 scan2 scan3 PAN[GLE]

TYPE

3 1

COMMENTS

The polarization angle (0.5tan (U/Q)) at each channel is calculated from scans I, Q, and U in that order.

NAME

PDEGREE

PURPOSE

Calculate the degree polarization at each channel from three scans containing Stokes paramters I,Q, and U.

SYNTAX

scan1 scan2 scan3 PDE[GREE]

TYPE

3 1

COMMENTS

The degree polarization at each channel is calculated from scans I, Q, and U in that order.

NAME

PEAK

PURPOSE

Locate the least squares two dimensional Gaussian peak of a header value for a group of scans as a function of their position on the sky.

SYNTAX

scan1 scan2 scan3 ... scan(n) PEA[K]

TYPE

n 1

COMMENTS

A two dimensional Gaussian peak is calcuated from a least squares solution to a sequence of header values as a function of position. Results of the fit are printed. The PEAK function is typically used for pointing data.

FUNCTION CONSTANTS

X VARIABLE header variable name to be used as x coordinate.

Y VARIABLE header variable name to be used as y coordinate.

Z VARIABLE header variable name to be used as z coordinate.

EXAMPLE

To calculate the pointing offset from a group of scans 5001 to 5005 taken from a continuum 5 point observation, use the INTEGRATE function to determine PEAK function on the data within S5. S5 = 5001 TO 5005 INTEGRATE ; S5 PEAK

NAME

PERROR

PURPOSE

Calculate the error on the degree of polarization from three scans containing Stokes paramters I,Q, and U.

SYNTAX

scan1 scan2 scan3 PAN[GLE]

TYPE

3 1

COMMENTS

The error in the degree polarization at each channel is calculated from scans I, Q, and U in that order. Note that the error of the Stokes parameters must have been previously calculated and stored using the BASELINE function.

NAME

PLOT

PURPOSE

Plot a spectrum, one pixel at a time.

SYNTAX

scan PLO[T]

TYPE

1 1

COMMENTS

PLOT displays the data within a scan, one pixel at a time. If the scan contains more than 1 pixel, data from a pixels are displayed.

FUNCTION CONSTANTS

CONTROL ten coded digits controlling physical parameters of the plot (0422851530)

CONTROL digit description

1 = 0 - no grid lines drawn across center of plot = 1 - grid lines drawn across center of plot

2 = 1 - points = 2 - solid lines = 3 - points + solid lines = 4 - histogram

3 4010 x coordinate of lower left corner of grid in units of 100

4 4010 y coordinate of lower left corner of grid in units of 100

5 x length of graph in 4010 coordinates in units of 100

6 y length of graph in 4010 coordinates in units of 100

7,8 size of numbers along x and y axes

9,10 size of labels

EXAMPLE

To display spectrum within scan 6096, type: 6096 PLOT If scan 7502 contain 30 pixels, to display the 30 spectra one at a time type: 7502 PLOT

NAME

PRINT

PURPOSE

Print values of header and/or data for a scan.

SYNTAX

scan PRI[NT]

TYPE

1 1

COMMENTS

Data is printed according to order, left to right, of digits described below. The printer device is set by the FILES function.

FUNCTION CONSTANTS

PRINT CODE Specifies the printed output and the ordering. If the code > 0, there will be a line space before printing each observation and descriptive heading will also be given.

1 all header data will be printed in raw form

2 weights and Y values

3 labelled header

4 line parameters measured by LINE function

5 system parameters

6 printer plot

7 positional information

8 source name and MESSAGE

9 frequency information

NAME

RD

PURPOSE

Remove a subdirectory within the S file.

SYNTAX

RD SUBDIR

TYPE

1 1

COMMENTS

When initialized, the S file contains 16 subdirectories, labelled S1, S2, ... S16. A user can dynamically create additional subdirectories with any 3 character label which does not conflict with function names, synthetic definitions, or other subdirectories. A user can remove a subdirectory which was previously created with the MD command. All data within the the deleted subdirectory is lost.

EXAMPLE

To remove a subdirectory labelled MHH RD MHH

NAME

READ

PURPOSE

Read data from SPA format magnetic tape

SYNTAX

scan REA[D]

TYPE

1 1

COMMENTS

Read a given scan from the magnetic tape file (MT01 - MTnn) selected by FILES function. Before the READ operation can be executed on a tape, the TAPE function must have been previously used to set up the tape and read the directory at the beginning of the tape.

EXAMPLE

To read scans 1001 to 1050 from a magnetic tape and place results into sub directory S1, type: S1 = 1001 to 1050 READ If sequential mode has been selected by the FILES function, then to read the 53rd to 75th scan in the current tape file and to store these in S10, type: S10 = 53 to 75 READ

NAME

REST

PURPOSE

Change the x coordinate axis to the rest frequency.

SYNTAX

scan REST

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed to the rest frequency. This change is reversible at any time.

HEADER CHANGES

KX

NAME

RUN

PURPOSE

Generate a new scan from a run of a header variable from a group of scans as a function of another header variable.

SYNTAX

scan RUN

TYPE

n 1

COMMENTS

A scan is generated from a run of a single header variable as a function of another header variable of a group of scans.

FUNCTION CONSTANTS

X VARIABLE header variable name to be used as independent variable

Y VARIABLE header variable name to be used as dependent variable XLOWER XUPPER

ORDER order of interpolation in final scan

EXAMPLE

To see how the header variable YSIGMA varies with system temperature (TS) for a group of scans in S10 and store the result in S11 S11 = S10 RUN PLOT

HEADER CHANGES

NIN, IN1, LENSCAN, XCH1, DCHDIN

NAME

SCALE

PURPOSE

Scale the Y values of a scan using Y values of scaling scan

SYNTAX

scan SCALE

TYPE

1 1

COMMENTS

SCALE is useful if one wishes to scale all the data as a function of some header variable. The scaling scan is generally created by the RUN function.

FUNCTION CONSTANTS

SCALING SCAN scan number in current directory which contains

SCALING VARIABLE header variable name in argument scan to

NAME

SECOND

PURPOSE

Extract data from the third spectrometer within a multi configuration of spectrometers.

SYNTAX

scan SEC[OND]

TYPE

1 1

COMMENTS

For data taken with several backends, these functions extract data taken within the respective spectrometer within the observed configuration. Once a spectrometer has been selected, it is not possible to extract data of the other spectrometers except by recalling the original data.

EXAMPLE

To extract data from the Q15 spectrometer in the observed configuration (Q23 Q15 QEF) of scan 7812, type: 7812 SECOND

HEADER CHANGES

NIN, IN1, KBE, LENSCAN, XCH1, XVEL1, XFR1, DCHDIN, DVELDIN, DFRDIN

NAME

SEQUENCE

PURPOSE

Change the scan number of a scan.

SYNTAX

scan SEQ[UENCE]

TYPE

1 1

COMMENTS

The scan number of a scan is changed to that specified by the sequence function constants SCAN and STEP. The original scan number SCAN is stored in a reserved location ISCOLD in the header. It can be restored to the scan with

FUNCTION CONSTANTS

SCAN value of new scan number

STEP incremental increase in SCAN between two successive of STEP after the new scan number has been put in the header location SCAN.

EXAMPLE

To copy scans 7526, 7829 and 8111 located in s4 to s10 and rename these scans 2001, 2002 and 2003 s10 = s4 seq

HEADER CHANGES

SCAN

NAME

SHOW

PURPOSE

Display spectra of a group of scans on the same plot. RMS noise.

SYNTAX

scan1 scan2 scan3 ... scan(n) SHO[W]

TYPE

1 1

COMMENTS

Spectra from a group of scans are displayed on the same plot. Each additional scan is displaced on the y axis by an amount DY. For scans which contain more than one pixel, a new plot is constructed for each additional pixel.

FUNCTION CONSTANTS

DY increment in Y by which successive plots are displaced

CONTROL ten coded digits controlling physical parameters of the plot (0422851530)

Control digit Description

1 = 0 - no grid lines drawn across center of plot = 1 - grid lines drawn across center of plot

2 = 1 - points = 2 - solid lines = 3 - points + solid lines = 4 - histogram

3 4010 x coordinate of lower left corner of grid in units of 100

4 4010 y coordinate of lower left corner of grid in units of 100

5 x length of graph in 4010 coordinates in units of 100

6 y length of graph in 4010 coordinates in units of 100

7,8 size of numbers along x and y axes

9,10 size of labels

NAME

SIGNAL

PURPOSE

Change frequency scale to signal band for frequency switched data.

SYNTAX

scan SIGNAL

TYPE

1 1

COMMENTS

The frequency scale of a scan taken by frequency switching is changed to the signal band. These changes are reversible at any time.

HEADER CHANGES

NAME

SINE

PURPOSE

Subtract a sine wave from the argument observation and calculate RMS noise.

SYNTAX

scan SIN[E]

TYPE

1 1

COMMENTS

The period, phase, and amplitude are determined from a least squares fit to the observational data within the specified intervals. After the fitted baseline has been subtracted, the rms noise level is calculated for data within the specified intervals and stored in the header as YSIGMA.

FUNCTION CONSTANTS

WAVELENGTH initial guess of wavelength of standing wave

EXAMPLE

To subtract a sine wave from scan 6756, type: 6756 SINE

HEADER CHANGES

YSIGMA, QYSIG

NAME

SKY

PURPOSE

Convert continuum raster scan x coordinate to position on the sky.

SYNTAX

scan SKY

TYPE

1 1

COMMENTS

The x axis of a scan generated from a raster continuum map is converted to positions on the sky.

HEADER CHANGES

XCH1, DCHDIN, KX

NAME

SMOOTH

PURPOSE

Applies a smoothing filter to the spectrum.

SYNTAX

scan SMO[OTH]

TYPE

1 1

COMMENTS

The spectrum is averaged over channel to the desired resolution in order to reduce the noise.

FUNCTION CONSTANTS

FILTER 0 - channel average 1 - boxcar 2 - Gaussian weights 3 - Hamming 4 - bin weighting

RESOLUTION resolution of filter function in units of the current x variable. XLOWER XUPPER

NAME

SORT

PURPOSE

Rearrange the argument list by sorting of a header variable.

SYNTAX

scan1 scan2 scan3 ... scan(n) SOR[T]

TYPE

n n

COMMENTS

The argument list is rearranged by sorting a one or two header variables in increasing or decreasing order. The function is useful in isolating scans with a given header value.

FUNCTION CONSTANTS

NUMBER OF VARIABLES SORT 1 or 2

PRIMARY VARIABLE NAME name of the header variable.

PRIMARY VARIABLE DIRECTION sort in increasing or decreasing value

SECONDARY VARIABLE NAME name of the header variable.

SECONDARY VARIABLE DIRECTION sort in increasing or decreasing value

EXAMPLE

To rearrange a group of scans in S1 by DALP positions and put this order of scans in S10, type: S10 = S1 SORT

NAME

SOURCE

PURPOSE

Rearrange the argument list by isolating scans within a specified tolerance of distance from each other.

SYNTAX

scan1 scan2 scan3 ... scan(n) SOU[RCE]

TYPE

n n

COMMENTS

A list of n argument scans is resolved into a series of separate source positions. All scans at common positions within a specified tolerance are listed together. The arguments are rearranged in the order listed and may be stored in a sub-directory in this order.

FUNCTION CONSTANTS

TOLERANCE tolerance in arcminutes for RA and DEC positions in a common source cluster

EXAMPLE

To rearrange a group of scans in S1 by common positions and put this order of scans in S10, type: S10 = S1 SOURCE

NAME

SV

PURPOSE

Display spectra of a group of scans in a spatial-velocity diagram.

SYNTAX

scan1 scan2 scan3 ... scan(n) SV

TYPE

n n

COMMENTS

Spectra which have been previously sorted on a header variable are displayed as a spatial velocity diagram. All spectra must cover the same range along the x axis. The magnitude of Z at each x and y in this diagram is represented by either dotted shading or contour lines. The user can input contour levels by setting the constants BOTTOM LEVEL and TOP LEVEL equal. For multi pixel scans, use the MASK function to identify a row, column, or diagonal. SV can also be used to display a continuum raster scan observation in which data from a row is contained within a scan.

FUNCTION CONSTANTS

Y COORDINATE name of header variable to be used as Y variable

CONTROL ten coded digits controlling physical parameters of the plot (0422851530).

LEFT left boundary of grid.

RIGHT right boundary of grid.

BOTTOM bottom boundary of grid.

TOP top boundary of grid.

CONTROL digit description

1 = 0 - no grid lines drawn across center of plot = 1 - grid lines drawn across center of plot

2 = 1 - z values printed on graph = 2 - points = 3 - lines connecting points = 4 - labelled contours = 5 - unlabelled contours = 6 - dense shading = 7 - optimum density shading = 8 - less dense shading = 9 - lowest density shading

3 = 4010 x coordinate of lower left corner of grid in units of 100

4 = 4010 y coordinate of lower left corner of grid in units of 100

5 = x length of graph in 4010 coordinates in units of 100

6 = y length of graph in 4010 coordinates in units of 100

7,8 = size of numbers along x and y axes

9,10 = size of labels

EXAMPLE

To display spectra in sub directory S1, type: S1 SV If S2 contains multi pixel data, use the MASK function with SV, S2 MASK SV

NAME

SYNTHETIC

PURPOSE

Print the current list of user defined synthetic functions

SYNTAX

SYN[TH]

TYPE

1 1

COMMENTS

The complete list of user defined functions are printed. The user is then prompted whether to reinitialize these definitions.

NAME

TAPE

PURPOSE

Function for mounting and handling of magnetic tapes

SYNTAX

TAPE

TYPE

1 1

COMMENTS

An SPA format magnetic tape is prepared for use with the READ and WRITE commands. Upon opening the device, the tape is probed to determine the tape type, reads an informational record, and then reads the tape directory. If for some reason the directory was destroyed, it can be recreated by answering yes to the request of listing the tape. The TAPE function is also used for writing the current tape directory to the magnetic tape itself.

NAME

THIRD

PURPOSE

Extract data from a spectrometer within a multi configuration of spectrometers.

SYNTAX

scan THI[RD]

TYPE

1 1

COMMENTS

For data taken with several backends, these functions extract data taken within the respective spectrometer within the observed configuration. Once a spectrometer has been selected, it is not possible to extract data of the other spectrometers except by recalling the original data.

EXAMPLE

To extract data from the QEF spectrometer in the observed configuration (Q23 Q15 QEF) of scan 7812, type: 7812 THIRD

HEADER CHANGES

NIN, IN1, KBE, LENSCAN, XCH1, XVEL1, XFR1, DCHDIN, DVELDIN, DFRDIN

NAME

TRANSFER

PURPOSE

Transfer data from one sub directory to another.

SYNTAX

scan REA[D]

TYPE

1 1

COMMENTS

This is actually a dummy function not often used explicitly. It is inserted by the program where necessary in commands. Thus, the command S2 = 1050 is altered by the interpreter to be S2 = 1050 TRANSFER

EXAMPLE

To transfer all scans within sub directory S14 to subdirectory S5, S5 = S10

NAME

UNSEQUENCE

PURPOSE

Reverses a previous sequencing operation by putting the header variable ISCOLD back in the header location.

SYNTAX

scan UNS[EQUENCE]

TYPE

1 1

COMMENTS

The scan identification of the data when the data was taken is kept in the header variable ISCOLD. UNSEQUENCE is valuable when for some reason, i.e. sorting, and the data was sequenced, and one wishes to return to the original scan ID,

EXAMPLE

To rename scans 11001 to 11050 to the original scan numbers

NAME

USB

PURPOSE

Recalculate frequencies and velocities for lower sideband.

SYNTAX

scan USB

TYPE

1 1

COMMENTS

Frequencies and velocities are calculated for upper sideband. These changes are reversible at any time.

HEADER CHANGES

XVEL1, DVELDIN, XFR1, DFRDIN, KLO

NAME

VLSR

PURPOSE

Change the x coordinate axis to velocity with respect to the local standard of rest.

SYNTAX

scan VLSR

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed to VLSR. This change is reversible at any time.

HEADER CHANGES

KX

NAME

VSUN

PURPOSE

Change the x coordinate axis to heliocentric velocity.

SYNTAX

scan VSUN

TYPE

1 1

COMMENTS

The nature of the x coordinate of a scan is changed to heliocentric This change is reversible at any time.

HEADER CHANGES

KX

NAME

WRITE

PURPOSE

Write data to SPA format magnetic tape

SYNTAX

scan WRI[TE]

TYPE

1 1

COMMENTS

Archive a scan to a magnetic tape file (MT01 - MTnn) selected by FILES function. Before the WRITE operation can be executed on a tape, the TAPE function must have been previously used to set up the tape and read the directory at the beginning of the tape. To update the directory on the tape itself, run the TAPE command and answer yes to the prompt "DO YOU WISH TO WRITE A DIRECTORY?" before exiting SPA.

EXAMPLE

To write scans 1001 to 1050 to magnetic tape 1001 to 1050 WRITE To write all scans in sub directory S9 S9 WRITE

BUGS

The SPA tape format is not compatible with SCSI Magnetic tape drives on UNIX operating systems since an EOF is automatically written after each record and after a tape repositioning command. Since this is exactly what happens after the tape directory is written at the beginning of the tape, a double EOF, or end of tape is created, nullifying all remaining data.

NAME

YHISTOGRAM

PURPOSE

Generate a histogram of Y values of a scan.

SYNTAX

scan YHIS[TOGRAM]

TYPE

1 1

COMMENTS

A histogram is generated from the y values of a scan and placed in the X register.

FUNCTION CONSTANTS

EXAMPLE

To see the distribution of the channels in scan 7562, type: 7562 YHISTOGRAM PLOT

HEADER CHANGES

NIN,IN1,KX,NHORN,LENSCAN,XCH1,DCHDIN

}