1 AUTO
             OBS\AUTO Time TWEAK|NOTWEAK

         Starts a simple auto-correlation measurement,  optionally  preceded
    by a tweak (sampling level adjustment) of the spectral correlator.  Time
    defines the integration  time  in  seconds.   The  continuum  correlator
    output is used to derive further Van Vleck corrections.

1 BANDPASS
             OBS\BANDPASS [Time]

         Start a specific procedure to calibrate instrumental phases of  the
    spectral  correlator.   Default  integration  time  is  5  seconds.  The
    spectral correlator is automatically connected to  a  noise  source  for
    this  purpose.   Delay  and  phase  tracking  are  cancelled  during the
    measurement.

1 CALIBRATE
             OBS\CALIBRATE [COLD]

         Starts an atmospheric amplitude calibration.   The  calibration  is
    done  by  measurements  on  the  absorber, on the sky, and optionally on
    the internal cold load when  argument  COLD  is  given,  by  moving  the
    receiver  tables  and  mirrors.  An extra attenuation can be inserted in
    the  receiver  1  when  measuring  the  power  on  the  absorber;   this
    attenuation   is   specified   by   command  OBS\SET  ATTENUATION.   The
    calibration mode can be specified by the OBS\SET CALIBRATION command.

         In INTERferometric  mode,  the  Correlators  and  the  total  power
    Detectors  are  used.  The spectral correlator is always tweaked in this
    procedure.

         This command is not available in OPTICAL or TEST modes.

1 CANCEL
                  OBS\CANCEL [CANCEL|KILL|STOP]

         The command CANCEL interrupts the data acquisition process.

            OBS\CANCEL

    Cancels current scan loop.  Data acquisition is stopped at  end  of  the
    next   subscan.   A  CANCEL  is  implicitely done by C in multi subscans
    procedures, such as FOCUS, POINTING and SKYDIP.

            OBS\CANCEL KILL

    Aborts current scan.  Data acquisition is stopped as  soon  as  possible
    (depending on observing procedure) and the data are flagged "Deleted" in
    the output file.  CANCEL KILL may be used  after  C  has  been   pressed
    during  a multi subscans command (FOCUS, POINTING, or SKYDIP).  A CANCEL
    KILL is implicitely done by a command MICRO.

            OBS\CANCEL STOP

    Requests reduction programs (RDI and AFF) to stop.

            OBS\CANCEL WAIT

    Allows OBS to proceed when it would normally  say  ``Waiting  for  ...''
    This command has to be used only when something abnormal happened in the
    acquisition (e.g. RDI crash).

1 CATALOG
                  OBS\CATALOG [SOURCE|LINE|PHASE] Name

         Select a new  catalog  for  sources,  line  frequencies,  or  phase
    calibrators.  Default catalogs are
         Sources   INTER_BASE:IRAM.SOU
         Line      INTER_BASE:IRAM.LIN
         Phase     INTER_BASE:PHASE.SOU
1 CORRECTIONS
                  OBS\CORRECTIONS Caz Cel [Focus] [/ANTENNA Iant]

         Enters pointing corrections and the focus zero  for  antenna  Iant.
    Caz  and  Cel  are  offsets  from  respectively -COH and -COV, the radio
    collimations, while Focus is an offset from HFO0 the nomi focus.   Using
    *  instead of a numerical value means do not change this parameter.  Caz
    and  Cel  are  in  arcseconds,  while  Focus  is  in  millimeters.    In
    single-dish mode, Iant defaults to the single-dish antenna


    Command CORRECTIONS is intended to be used for temporary  changes  only,
    for  example  to  help  in  a pointing session, or to refine the current
    pointing on a particular source.   Corrections  are  remembered  by  OBS
    using  the  MEMORY.OBS procedure, and NOT reset to 0 by a SET\OBSERVE or
    SET\POINTING command.  To  change  permanent  pointing  parameters,  the
    SET\POINTING  command is recommended, and corrections should normally be
    set to zero.

1 DELAY
                  OBS\DELAY Dmin Dmax Dstep/ANTENNA Iant

         Starts a delay-scanning measurement on antenna Iant.  Dmin and Dmax
    are  the  minimum and maximum delays in nanosec.  Dstep is the scan rate
    in nanosec/sec.  The scanning  is  centered  around  the  current  delay
    offset.

1 DRIFT
                  OBS\DRIFT    [Length    Speed    Angle      [Integration]]
    [/HORIZON] [/BASIS]

         Define a continuum drift single-dish procedure.
    - Length is the length of the drift in current angle units.
    - Speed is the drift speed ins arcseconds per second of time.
    - Angle is the orientation angle of the drift in degrees, and the option
    /HORIZON  or  /BASIS  indicates  whether this angle is in the Horizontal
    coordinate system or in the current Basis coordinate  system.   Standard
    orientation angles are
       +AZ   -90 degrees
       -AZ   +90 degrees
       +EL     0 degrees
       -EL   180 degrees
    - Integration is the integration time for each  dump  of  the  continuum
    detectors in seconds.

1 FLUX
                  OBS\FLUX

          Start a cross-correlation (with default integration time) and  use
    default  antenna  efficiencies  to  determine  the  source flux density.
    Subsequent correlations on the same source will compare the measure flux
    density  with  this  value,  and  issue  a  warning in case of excessive
    losses.  This command should be used once on each  phase  calibrator  at
    start of a given project for proper monitoring.

1 FOCUS
                  OBS\FOCUS [Length [Npos]] [/ANTENNA A1 ...  An]

         In  INTERferometric   mode,   starts   an   interferometric   focus
    measurement.   A1 ...  An is the list of antennas to focus (default: all
    antennas).  Three or more antennas must be connected,  or  one  must  be
    fixed.  Npos  is  the number of focus position to check (3 or 5, default
    3).

         Length is the focus displacement in millimeter (default 2.0  at  86
    GHz).  The command is forbidden in OPTICAL or TEST modes.

1 GAIN
                  OBS\GAIN

         Starts a receiver gain-ratio measurement.  At least three  antennas
    are  required  for  this procedure.  This procedure is available only in
    INTERferometric   mode.   This   is   just   a    standard  correlation,
    but   identified   specially   to   help   data  reduction.  The current
    number of subscans is used.

1 HOLOGRAPHY
                  OBS\HOLOGRAPHY dAz dEl Length Speed Direction /ANTENNA [A1
    ... An]

         Start an holography measurement for  antennas A1 .. An.   Normally,
    only  one  antenna should be specified, but the command can also be used
    to initiate a drift to measure e.g. an  azimut  encoder.   This  command
    makes a drift in interferometric mode, centered around the specified dAz
    and dEl horizontal offsets.  Direction can be  +AZ,  -AZ,  +EL  or  -EL.
    Length  and  Speed  are  in  "  and "/sec respectively.  For example the
    following procedure could be used to make a complete 32x32 beam map :
        DEFINE INTEGER BEAM
        LET BEAM 56
        SET ANGLE SEC
        SET SUB 4
        OFFSET 0 0/HORIZON
        CALIBRATE
        START
        FOR I -16 TO 15 BY 1
            IF (MOD(I,2).EQ.0) THEN
                HOLOGRAPHY BEAM|2     I*BEAM|2 16*BEAM BEAM|8 +AZ/AN 1
            ELSE
                HOLOGRAPHY BEAM|2 (I+1)*BEAM|2 16*BEAM BEAM|8 -AZ/AN 1
            ENDIF
            OFFSET 0 0/HORIZON
            CALIBRATE
            START
        NEXT
1 LEVELS
                  LEVELS [Goal] [/READ]

         Adjust the receiver attenuators to optimize  the  total  power  and
    correlator  levels. Goal is the desired total power level, and should be
    between  100  and  200  (default  170,  giving  best  efficiency).   The
    adjustment  should  be  made  around  the  lowest elevation used for the
    observation.

         If option /READ is present, do not adjust the attenuator, but  read
    their values from the microprocessors.

1 LINE
                  LINE  Name  [Frequency  Band   [Lock   [Center   [Harm]]]]
    [/RECEIVER Irec]

         Specifies the observing frequency in MHz for all antennas.   If  no
    Frequency  is  given,  the  line is selected from the line catalog.  The
    catalog format is the same as the LINE command format.
         Frequency is the observing rest frequency in GHz.
         Band is USB or LSB
         Lock is HIGH or LOW.
         Center is the IF frequency (in MHz) corresponding to the  specified
    rest frequency.  Default is 350 MHz.
         Harm is the harmonic number used to generate the LO1 from the  LO2.
    By  default,  Harm is computed in order to give LO2 as close as possible
    to 1.875 GHz.

         The command is accepted in all modes, but sent  (by  command  LOAD)
    only     if     the     observing     mode   is   INTERferometric.   The
    relationship  between  the  various  frequencies  is  defined   in   the
    ``Frequency  Setup'' document, and summarized below.  (the signs defined
    according to the Band and Lock)
    3mm receiver
            FLO2 = (FSKY +|- CENTER +|- EPS) / (HARM +|- 1)
                       USB|LSB   HIGH|LOW          USB|LSB
    1.3mm receiver
            FLO2 = (FSKY +|- CENTER +|- 3*EPS) / (3*HARM +|- 1)
                       USB|LSB   HIGH|LOW              USB|LSB

    where   FSKY = FREST*(1-v/c) is the Doppler corrected frequency
            EPS  = 100 + 50/512
1 LOAD
                  OBS\LOAD [/AZIMUTH Dir] [/FREQUENCY]

         Loads observing parameters.  This command  sends  source  position,
    frequency  information,  and  a  number of other things to the telescope
    control program, but  data  acquisition  is  not  started.   A  LOAD  is
    implicitly done by all acquisition commands.

         The Option /AZIMUTH can be used to force antenna to  chose  a  slew
    direction;  Dir  can  be +AZ or -AZ.  A LOAD command is necessary before
    receiver tuning.  The Option /FREQUENCY will  only  send  the  frequency
    with Doppler corection for the new source, but without antenna movement.
1 MICRO
                  OBS\MICRO

         Aborts the current acquisition and put  all  antennas  under  Micro
    control.  To be used in case of emergency such as antenna oscillations.

1 OFFSETS
                  OBS\OFFSET Off\ Off\Beta [Off\Focus] [/HORIZON] [/BASIS]

         Defines source  or  focus  offsets  for  ALL   antennas.   Position
    offsets    are   in   the   current   angle   units.    In   the   BASIS
    coordinate system, they define the antenna and delay tracking center; in
    the HORIZONTAL coordinate system, only the antenna  tracking  center  is
    modified.  Focus offsets are in millimeters.

              OBS\OFFSET Off\ Off\Beta [/DELAY]

         Defines only the delay tracking offsets (a useful feature to  avoid
    artificial sources at the source position caused by correlator errors).

1 ONOFF
                  OBS\ONOFF Off1 Off2 [System] [/TIME Tsub] [/SUBSCANS Nsub]

         Start a on-off multi-dish procedure.  Tsub is the integration  time
    on  each  position  (subscan  duration).   Off1 and Off2 are the angular
    offsets (in current angle units) for the reference position, and  System
    is  the  coordinate  system in which they are defined (Horizon or Basis,
    default as specified in SET OFFSET).  Nsub is  the  number  of  subscans
    pair;  default  value  is the number of subscans defined for single-dish
    measurements.

         Auto correlation are made without tweaking.  Data is written in the
    the  compressed  file  INTER\COMP:Date.IPB)  using  the  following  CLIC
    procedure :
        CLIC\SET X IF
        CLIC\SET ANTENNA 1 2 3 4 ! As available
        CLIC\SET Y AUTO
        CLIC\FIND/PROC ONOF
        CLIC\PLOT
1 POINTING
                  OBS\POINTING [PSEUDO] [/ANTENNA A1 ...  An]
         [/FAST] [/LENGTH Length] [/AZIMUT +-Az] [/ELEVATION +-El]

         In  INTERferometric  mode,  starts  an   interferometric   pointing
    measurement   using   the   correlators in cross-correlation mode. Three
    or more antennas must be connected, or one must be fixed.  A1 ...  An is
    the list of antennas  to move (default:  all antennas moved).

    If argument PSEUDO is specified,  the  pointing  is  done  in  ``pseudo-
    continuum''   mode,  i.e.  in  auto  correlation.  One  subband  of  the
    correlator should have been selected to match a strong spectral line  in
    this case.

         Four drifts are made (Az increment, Az decrement, El increment,  El
    decrement).  The command is forbidden in OPTICAL and TEST modes.  Option
    /FAST can be used to  scan  twice  faster than  usual.   Option  /LENGTH
    can  be  given  to  modify the scanning length: the argument is actually
    half the scanning length in arcseconds.  Options /AZIMUT and  /ELEVATION
    can  be  used  to select which drifts are actually performed among the 4
    possible: +Az, -Az, +El, -El.

1 SAVE
                  OBS\SAVE

         The SAVE command creates a new version of the INTER\BASE:MEMORY.OBS
    file,  which  contains  current  values for antenna variables parameters
    (efficiencies, calibration parameters, current  source,  etc...).   This
    file  is  automatically executed each time OBS is activated, and updated
    each time OBS terminates.
1 SET
                  OBS\SET Parameter Value [/ANTENNA Iant]

    Specifies some observing parameter.

2 ANGLE
                  SET ANGLE Degree|Minute|Second|Radian

         Define the current angle unit

2 ARRAY
                  SET ARRAY A1 A2 A3

         Specifies the antennas currently available in  the  interferometer.
    SET ARRAY also indicates which antenna should be used for the MULTI-DISH
    mode.  This command is intended for temporary unavailability of antennas
    still   on  station.   The  CONFIGURE mode command SET\ANTENNA should be
    used otherwise.

2 AMBIENT
                  SET AMBIENT T_amb P_amb or SET AMBIENT Auto

         Defines the external temperature and pressure, or specifies use  of
    the meteo station.

2 ATMOSPHERE
                  SET ATMOSPHERE T_atm_s T_atm_i /ANTENNA Iant

         Defines the atmospheric temperatures in  signal  and  image  bands.
    This is required in the CAL MANUAL mode only.

2 BEAM_THROW
                  SET BEAM_THROW Bs /ANTENNA Iant

         Indicate the beam separations Bs  (in  arcsecond)  for  beam-switch
    observations.   This  is  a  hardware  value,  not a software controlled
    parameter.

2 CALIBATION
                  SET CALIBRATION AUTO|MANUAL|NONE|TREC /ANTENNA Iant

         Defines the calibration mode
    NONE:  uncalibrated spectra & data
    MANUAL:  Manual guess of atmospheric transmission
    AUTO:  fix Water, compute Trec
    TREC:  fix Trec, compute Water

2 CHOPPER
                  SET CHOPPER T_warm /ANTENNA Iant

         Defines the absorber chopper temperature for antenna Iant

2 DEBUG
                  SET DEBUG On|Off On|Off On|Off

         For authorized users only.

2 FORWARD
                  SET FORWARD F_eff /ANTENNA Iant

         Specifies the forward efficiency of antenna Iant.  Beam  efficiency
    is assumed equal to forward efficiency in all cases (antenna temperature
    scale).

2 GAIN_IMAGE
                  SET GAIN_IMAGE G /ANTENNA Iant

         Specifies the image to signal gain ratio for antenna Iant

2 HUMIDITY
                  SET HUMIDITY Humidity

         Specifies the humidity (for refraction  correction)  if  the  meteo
    station is not used.

2 INTEGRATION
                  SET INTEGRATION Time

            Specifies the integration times between  dumps  for  the  cross-
    correlation

2 LEVEL
                  SET LEVEL terminal file

         Specifies the level of printout  (0  many  messages,  2  Normal,  4
    extremely limited) for terminal and log file (INTER_LOG:Date.LOG-OBS).

2 MODE
                  SET MODE Imode [/ANTENNA Iant]

         Specifies the observing mode Imode, which can take the values

    INTERferometer:  Select interferometric observing mode,  allowing  AUTO,
    CALIBRATE, GAIN, FOCUS, POINTING, SKYDIP and Cross correlation observing
    procedures.  The correlators are used for pointing and focusing in cross
    correlation  mode.   In addition an ONOFF procedure allows spectra to be
    taken with all antennas at the same time.

    OPTICAL:  This mode is used for  optical  pointing.   The  only  allowed
    commands  are  SOURCE  and  LOAD  in  this  mode.   The optical pointing
    constants and refraction model are used for tracking.

    CONFIGURE:   This  mode  is  used  to  specify  a  change  of   hardware
    configuration, such as new position of antennas, new IF connections, new
    pointing constants, etc...  The OBS\ language becomes inactive, and  the
    SET\  language is turned on.  Observations can be resumed only using the
    SET\OBSERVE command.

    TEST:  This mode is used  for  tests  of  the  correlators.   LO1  Walsh
    switching,  phase  and  delay  tracking  are  suppressed.   The spectral
    correlator  is  automatically  connected  to  the  noise  source.    The
    continuum  correlator must be manually connected to another noise source
    to  be  tested.   Antennas  are  unused  and  several  commands   become
    unavailable in this mode.

2 OFFSETS
                  SET OFFSETS Basis|Horizon

         Specifies the coordinate system to be used for offsets.

2 OPACITY
                  SET OPACITY Tau_S Tau_I /ANTENNA Iant

         Specifies the atmospheric opacities in signal and  image  band  for
    antenna Iant.  Required only in CAL MANUAL mode.

2 SHOW
                  SET SHOW ON|OFF

         Selects or disables the "full-display".

2 SCAN
                  SET SCAN Ns

         Specifies the number of scans requested by each START command.

2 SUBSCAN
                  SET SUBSCAN Ns

         Specifies   the   number   of   subscans   for   each   scan.

2 TABLE
                  SET TABLE Sky

         Specifies  the  table  position  for  observation  on  Sky,  as   a
    percentage  of  total  displacement  (0 :  sky only, 100 absorber only).
    This value is common for all antennas.

2 TREC
                  SET TREC Trec /ANTENNA Iant

         Specifies the receiver temperature for antenna Iant.  Required only
    in CAL TREC mode.

2 WATER

               SET WATER wH2O

         Specifies  the  water  vapor  content   of   the   atmosphere   (in
    millimeter).  Required only in CAL AUTO mode.
1 SHOW
                  OBS\SHOW [* | Item]

       OBS\SHOW      : Refreshes the "full-screen" display
       OBS\SHOW *    : Lists all parameter values.
       OBS\SHOW item : List one parameter.

    The available parameters are
       ANGLE       D|M|S                 : Angle unit type
       AMBIANT     Tamb Pamb | AUTO      : Meteo parameters and mode
       ARRAY       List                  : Antennas in array
       ATMOSPHERE  T_atm_s T_atm_i       : Atmospheric temperature (*)
       ATTENUATION Att_1  Att_2          : Attenuation for calibration
       BEAM_THROW  Value                 : Chopper throw (*)
       CALIBRATION AUTO|MANUAL|NONE|TREC : Calibration mode (*)
       CHOPPER     T_warm T_cold         : Chopper temperatures (*)
       CORRECTIONS -COH -COV HFO0        : Pointing and focus corrections (*)
       DEBUG       On | Off              : Debug flags (for test only)
       FORWARD     F_eff                 : Forward (=Beam) efficiencies (*)
       FIT         On | Off              : Fit pointing scans ?
       GAIN_IMAGE  G                     : Gain/Signal band ratio (*)
       LEVEL       terminal file         : message priority level
       MODE                              : OBS operating mode
       OFFSETS     Basis | Horizon       : Offsets type
       OPACITY     Tau_S Tau_I           : Atmospheric opacities (*)
       PHASE       Atm | Noatm | Both    : Atmospheric phase compensation
       SCAN        Ns                    : Number of scans per START
       SUBSCAN     Ns                    : Number of subscan per scan
       TABLE       Sky                   : Table OFF position
       TREC        Trec Tsys             : Receiver and System temperature (*)
       WATER       wH2O                  : Water vapor content  (*)
    Parameters marked (*) may depend on antenna.  All antennas are listed in
    this case.

1 SKYDIP
                  OBS\SKYDIP Azi [/ANTENNA A1 ...  An]

         Starts a skydip measurement with the  specified  or  all  connected
    antennas   at  azimuth  Azi.   The  continuum  detectors  are  used.   A
    measurement on the tables  is  made  first  then  the  sky  emission  is
    measured  at  6  different  elevations  equally  spaced  in  air masses,
    starting from 45 degrees elevation.  The data is  written  in  the  .IPB
    file, and no real time reduction is available.

         The command is forbidden in OPTICAL and TEST modes.

1 SOURCE
                  OBS\SOURCE     Name      [Coordinates      ...]      /TYPE
    OBJECT|PHASE|BAND [/VELOCITY Vtype [Vvalue]] [/FLUX Fvalue]

         Selects a source of the specified  type:   OBJECT  for  sources  to
    study,  PHASE  for  Phase calibrator, BAND for Bandpass calibrator.  The
    SOURCE catalog is searched for OBJECT  type  sources,  while  the  PHASE
    catalog  is searched for PHASE and BAND sources.  Source coordinates may
    be in the command line, in the same format as the source catalog, i.e.

    NAME  Syst [Epoch] Lambda       Beta        Vtype  [Velo] [FLUX Value]
    W3OH  EQ   1950.0  02:23:16.50  61:38:57.0  LSR    -45.0   FLUX 3.73

    Where
         Syst is the coordinate system (EQ, HO, GA) and Epoch  its  optional
              epoch.
         Lambda and Beta are the coordinates (in hours and  degrees  for  EQ
              coordinates, in degrees only for HO and GA coordinates).
         Vtype is the reference frame (LSR,  EARTH,  HELIO,  or  NULL  which
              means no Doppler tracking) and Velo the velocity in km/s.
         FLUX is a keyword indicating a value for the continuum flux (in Jy)
              at 3mm.

         The /TYPE option is compulsory, and indicates in wich  catalog  the
    source  should be searched.  PHASE and BAND sources have a velocity type
    NULL to avoid changing the observing frequency between  the  source  and
    the calibrator.

         The /VELOCITY Vtype Vvalue and /FLUX Fvalue options can be used  to
    override the velocity or flux specified in the catalog.
1 SPECTRAL
                  OBS\SPECTRAL Unit Bandpass IF_2 [/CONTINUUM Band_C  LO2_C]
    [/RECEIVER Irec]

         Configures  the  spectral  correlator unit  number Unit.   Bandpass
    indicates  the contiguous  bandpass  to be used (20, 40, 80 or 160 MHz).
    IF_2 is the second IF frequency of the bandpass center. It is rounded to
    the nearest multiple of 0.625 MHz (the LO3 frequency step).

         The /CONTINUUM option specified which  bandpass  should be analyzed
    to  produce  the  temporal  data.   The default is  80 % of the original
    band.

         Option /RECEIVER is used to indicate to  which  receiver  the  unit
    should be connected.

1 STABILITY
                   OBS\STABILITY Time [TWEAK|NOTWEAK]

         Perform an autocorrelation of specified  integration  time  on  the
    calibration  table  ("Hot"  load),  and  analyse  the result in terms of
    receiver stability. Time should be at least 60 sec.

1 START
                  OBS\START

         In  INTERferometric  or  TEST  mode,  starts  a   cross-correlation
    measurement, using the number of scans and subscans specified by the SET
    SCANS and SET SUBSCANS commands and integration time  specified  in  SET
    INTEGRATION.

1 END




























