idm_source_path='/hao/aim2/dmsp/dmsp_idm_4s/';
idm_file = 'l1301121a.txt';
folder = '0105/';
filename = strcat(idm_source_path,folder,idm_file); 
fid = fopen(filename,'r');
instr_date = fgets(fid);
data = dlmread(filename,'',2,0);
IDMFile = struct('data',data,'instrument',str2double(instr_date(2:3)),'year',str2double(instr_date(4:5)),...
    'doy',str2double(instr_date(6:8)),'minute', str2double(instr_date(9:10)),'sec', str2double(instr_date(11:12)),...
    'UT',data(:,1),'HzFl',data(:,2),'VtFl',data(:,3),'StdDevHz',data(:,4),'StDevVt',data(:,5),'ElctroPot',data(:,7),...
    'MLAT',data(:,8),'MLT',data(:,9),'GLAT',data(:,11),'GLON',data(:,12));