TRACE Analysis Guide

Peter Young, GSFC

Updated: 16-Apr-2026. I saw that this guide was very out of date, so I've made some updates.

This page gives some information about using TRACE data in IDL.

Resources

TRACE analysis guide at LMSAL

Downloading data

Use the VSO to get the files. For example:

s=vso_search('29-sep-2002 06:30','29-sep-2002 06:45',inst='trace',wave=171)
a=vso_get(s)

Other wavelength options are: 195, 284, 1600 and 5000 (white light).

The data provided by the VSO are fully calibrated, so there's no need to "prep" the data. Simply read the files with read_trace.

Reading data

Via read_trace

After downloading from VSO, you can read the files directly into an index-data pair by doing:

read_trace,files,-1,index,data

Since your file list may contain a mixture of wavelengths, you can do some filtering with the trace_sswhere GUI:

read_trace,files,-1,index
ss=trace_sswhere(index)
read_trace,files,ss,index,data

To convert to IDL maps, just do:

index2map,index,data,map

Via the TRACE catalog

The TRACE catalogue is stored in $SSWDB/tdb and comes in three forms: tcl (standard catalogue), tcs (short catalogue) and tce (engineering catalogue). Make sure you have the tdb directory in your $SSWDB distribution.

Reading and displaying the catalogue files is done as follows:

trace_cat,'31-may-98','1-jun-98',cat
more, trace_list_index(cat)

and the index and data arrays can be loaded as follows:

trace_cat2data,cat,index
ss=trace_sswhere(cat)
trace_cat2data,cat(ss),index,data

Avoiding bad data

Quite a large proportion of TRACE data is almost unusable because of the spikes in the data. One can avoid choosing these data by making use of the .img_dev tag in the index structure, e.g.,

ss=where( index.img_dev le 70. )

Calibrating

To use trace_prep, you need to have the dark current files. These are distributed through $SSWDB.

The standard call to trace_prep is

IDL> trace_prep,index,data,outindex,outdata,/unspike,/destreak,/deripple

Co-aligning images

This can be done with

IDL> trace_align_cube, itrace, dtrace, index, data

where itrace and dtrace are the initial index and data fields, and index and data are the outputs.

Page maintained by Dr Peter R Young.