orbit-idl-2: 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 CentOS possible default full paths are:

/usr/bin/orbit-idl-2 - from package: ORBit2-devel

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/orbit-idl-2 - from package: orbit2

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

Error in other languages:
orbit-idl-2: bevel nie gevind nie
orbit-idl-2: comandă negăsită
orbit-idl-2: comando não encontrado
orbit-idl-2: commande introuvable
orbit-idl-2: command not found
orbit-idl-2: käsku ei ole
orbit-idl-2: không tìm thấy lệnh
orbit-idl-2: komanda nerasta
orbit-idl-2: Kommando nicht gefunden.
orbit-idl-2: kommandot finns inte
orbit-idl-2: komut yok
orbit-idl-2: nie znaleziono polecenia
orbit-idl-2: níor aimsíodh an t-ordú
orbit-idl-2: no se encontró la orden
orbit-idl-2: no s'ha trobat l'ordre
orbit-idl-2: opdracht niet gevonden
orbit-idl-2: parancs nem található
orbit-idl-2: perintah tidak ditemukan
orbit-idl-2: príkaz nenájdený
orbit-idl-2: příkaz nenalezen
orbit-idl-2: команда не найдена
orbit-idl-2: командата не е открита
orbit-idl-2: 命令找不到
orbit-idl-2: コマンドが見つかりません