public static function caliperSend($caliperBody, $content_type='application/json', &$debug_log=false)
    {

        $caliperURL = LTIX::ltiRawParameter('custom_sub_canvas_xapi_url');
        if ( strlen($caliperURL) == 0 ) {
            if ( is_array($debug_log) ) $debug_log[] = array('custom_sub_canvas_xapi_url not found in launch data');
            return false;
        }

        $key_key = self::ltiParameter('key_key');
        $secret = self::decrypt_secret(self::ltiParameter('secret'));

        $retval = LTI::sendJSONBody("POST", $caliperBody, $content_type,
            $caliperURL, $key_key, $secret, $debug_log);
        return $retval;
    }