ossim-modopt: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/ossim-modopt - from package: ossim-core

You may install the required package with command apt-get install {package}

Error in other languages:
ossim-modopt: bevel nie gevind nie
ossim-modopt: comandă negăsită
ossim-modopt: comando não encontrado
ossim-modopt: commande introuvable
ossim-modopt: command not found
ossim-modopt: käsku ei ole
ossim-modopt: không tìm thấy lệnh
ossim-modopt: komanda nerasta
ossim-modopt: Kommando nicht gefunden.
ossim-modopt: kommandot finns inte
ossim-modopt: komut yok
ossim-modopt: nie znaleziono polecenia
ossim-modopt: níor aimsíodh an t-ordú
ossim-modopt: no se encontró la orden
ossim-modopt: no s'ha trobat l'ordre
ossim-modopt: opdracht niet gevonden
ossim-modopt: parancs nem található
ossim-modopt: perintah tidak ditemukan
ossim-modopt: príkaz nenájdený
ossim-modopt: příkaz nenalezen
ossim-modopt: команда не найдена
ossim-modopt: командата не е открита
ossim-modopt: 命令找不到
ossim-modopt: コマンドが見つかりません