GATHER_XY(1)

          T_CLOSE={2minutes}
          T_NEAR={25minutes}
          IM_SCALE={1.97784}
          limb={limb datasets}
          fd={full disk Intens datasets}
          fluxb={flux budget datasets}
          loi={LOI_I datasets}
          table={default table dataset}
          out={position info datasets}

DESCRIP-

TION

Gather_xy

is

a

stra-

tegy

module

that

col-

lects

MDI

point-

ing

infor-

ma-

tion

from

MDI

struc-

ture

pro-

gram

Flux

Budget,

LOI_I

and

limb

data

and

from

Dynam-

ics

full

disk

inten-

sity

data.

Gather_xy

pro-

duces

a

pair

esti-

mate

of

the

loca-

tion

of

the

MDI

images

center.

Gather_xy

exam-

ines

four

pos-

si-

ble

sources

of

posi-

tion

info:

  Limb data from the structure program.  The limb data is time-filtered
        on-board with a 24 minute filter and sampled each 12 minutes.
        The limb data is assumed to be first processed by another program
        which places the disk center position in keywords X0, Y0.
        Gather_xy takes these keywords and copies them into LIMB_X0 and
        LIMB_Y0 respectively, if the input datasets of limb data are
        present.

  Full Disk Continuum or Line-Depth data.  The full disk data is sampled
        each minute.  Another program will process the data and create
        parameters X0, Y0 which contain the disk center position.
        Gather_xy will take those values and copy them into FD_X0 and
        FD_Y0 respectively.  They will then be smoothed with the same
        24 minute filter used on-board for the limb data.  The values
        SMFD_X0 and SMFD_Y0 will be produced.

  Flux Budget data.  The 128x128 Flux Budget data is time averaged
        continuum intensity data that is averaged with the standard 24 minute
        filter on-board.  The center position will be computed by another
        program and placed into the usual X0, Y0 pai.  Gather_xy will
        copy these into FB_X0 and FB_Y0.

  LOI_I data.  The "LOI" data averaged by MDI is sampled each minute and
        will likely be the most complete dataset available since it is
        sent redundantly.  The computed X0, Y0 will be copied into
        LOI_X0 and LOI_Y0 them smoothed into SMLOI_X0, SMLOI_Y0.

  A table manually maintained with times and positions is also available.

posi-

tion

info

and

deduce

a

"Best"

loca-

tion

accord-

ing

to

the

fol-

low-

ing

rules.

First,

a

"near

enough"

time

is

used

to

decide

if

the

avail-

able

posi-

tion

info

has

at

least

3 sam-

ples

near

enough

to

use

in

a

spline

inter-

po-

la-

tion.

If

not,

values

are

exam-

ined

in

the

order:

LIMB,

SMFD,

FB,

SMLOI.

The

first

choice

is

to

find

at

least

three

points

within

+-

BT_NEARR.

If

found,

these

will

be

used

for

a

spline

inter-

po-

la-

tion

to

the

desired

time.

Second,

a

sin-

gle

value

within

+-

BT_CLOSER

will

be

serached

source

will

be

exam-

ined.

If

none

of

the

meas-

ured

values

are

avail-

able,

the

value

from

the

table

which

is

the

closest

preceed-

ing

value

will

be

used.

Since

the

table

is

intial-

ized

with

(512,512)

at

launch,

there

will

always

be

a

value

selected.

The

source

of

the

adopted

a

posi-

tion

value

(pair)

it

will

put

that

value

into

BEST_X0,

BEST_Y0.

All

of

the

X,Y

posi-

tions

assumed

to

be

in

a

coor-

di-

nate

sys-

tem

where

the

first

pixel

in

the

array

is

labelled

0,0

and

the

loca-

tion

refers

to

the

opt-

i-

cal

center

of

use

of

the

IM_SCALE

param-

e-

ter.

The

full_disk

IM_SCALE

param-

e-

ter

used

for

com-

parison

can

be

changed

on

the

com-

mand

line.

The

X

axis

is

presumed

to

be

the

first

set

of

con-

tigu-

ous

pix-

els

found

in

the

array.

Gather_xy

exam-

ines

and

processes

only

pro-

duces

data

for

all

of

the

times

implied

by

the

out-

put

dataset

spec.

If

the

out-

put

dataset

over-

view

file

already

exists,

the

out-

put

dataset

is

presumed

to

already

exist

and

will

be

modi-

fied

by

pos-

si-

bly

new

data

pro-

vided.

If

observed

values

are

present

replaced

by

new

values

fol-

low-

ing

the

same

NEAR

and

CLOSE

rules,

they

will

be

retained.

All

pro-

vided

input

sources

will

be

exam-

ined

and

the

correspond-

ing

values

updated.

In

nor-

mal

usage,

gather_xy

will

be

used

to

gen-

erate

a

dataset

con-

sist-

ing

only

of

the

"BEST"

values.

Each

dataset

will

be

a

TS_EQ

type

with

default

values

of

30 second

T_STEP

and

1 day

T_BLOCK.

The

out-

put

series

number

and

T_EPOCH

will

be

used

for

the

time

refer-

ence.

The

T_OBS

param-

e-

ter

will

be

filled

with

the

T_OBS

from

the

selected

source.

In the Overview File, at least:

  T_EPOCH
  T_START
  T_STOP
  T_FIRST
  T_LAST
  T_BLOCK
  T_STEP
  T_CLOSE
  T_NEAR
  IM_SCALE
  CONFORMS
  DATAKIND
  PROTOCOL

In the record info file:

  T_REC
  T_XY
  BEST_X0
  BEST_Y0
  XYSOURCE
  LIMB_X0
  LIMB_Y0
  LIMB_T
  LIMB_IX0
  LIMB_IY0
  LIMB_IT
  FD_X0
  FD_Y0
  FD_T
  SMFD_X0
  SMFD_Y0
  FB_X0
  FB_Y0
  FB_T
  FB_IX0
  FB_IY0
  FB_IT
  LOI_X0
  LOI_Y0
  LOI_T
  SMLOI_X0
  SMLOI_Y0