orbit-idl: 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 - from package: ORBit-devel

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

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