EOL Aircraft Field Project Computing Handbook
Contents
1. Integrating to the RAF Aircraft Computing Infrastructure
1.1. Hooking up to the onboard network
There are two separate Gigabit ethernets onboard. One is for data collection and the second is for data display. The two nets are connected through the central server, which provides DHCP to both networks.
- 192.168.184.0 is for RAF data collection. Users will not typically connect to this network.
- 192.168.84.0 is the display and general purpose network. The network switch on this subnet provides Power over Ethernet (PoE).
1.2. Timing (onboard)
There are 3 possible methods of acquiring time. Each aircraft has a Symmetricom SyncServer 250.
Network Time Protocol (NTP)
- Accurate to a few milliseconds.
Hostname is 'timeserver' and is available on both networks. Addresses 192.168.84.10 & 192.168.184.10.
Symmetricom has a WindowsXP client if you want something different from the WindowsXP default.
Wits, a program to edit XP registry to set the NTP parameters. By default XP only updates once per day.
Another tool to setup the WinXP NTP client, with a clock.
IRIG-B 123 (AM) standard. Definition PDF
- Accurate to a few microseconds.
- This will require the purchase of an IRIG-B card.
- Wallplate feeds are available throughout the aircraft.
Pulse per Second (1-PPS)
- Wallplate feeds are available throughout the aircraft.
It may be possible to get your own GPS antenna feed.
- Make sure to request this far enough in advance.
1.3. Real-time data feed onboard
NCAR will be distributing the IWGADTS recommended data packet on all aircraft.
- Currently UDP broadcast to 192.168.84.255 and 192.168.184.255 on port 31000.
- UDP to RS-232 converters can be provided. Request in advance as they need to be mounted.
- This packet has a 2-3 second delay between data acquisition and receipt to users.
- The time tag is of data acquisition.
1.4. Acquiring data from the database
EOL is using the PostgreSQL database for real-time data access and display.
Aircraft/DatabaseTables Current layout of database tables.
Aircraft/SQLExamples Some C program examples to access the database.
- On-board
- Ground
1.5. Instrument Control
A central instrument control infrastructure for our DSMs is still under design for onboard instrument control.
- Web interface onboard.
- We are still designing this.
EOL will not provide any infrastructure for remote instrument control other than providing bandwidth. SATCOM is still not reliable enough for mission critical remote instrument control.
- IRC-bot
- Best current option for control between ground and aircraft.
- Low delay.
- You are probably already using chat to communicate with participants.
- Easy, simple text commands can be used.
- Best current option for control between ground and aircraft.
- LDM files.
- Long delay (30-60 seconds).
1.6. Reporting Instrument Status
Instruments wishing to provide a status web-page can multicast the below XML packet to 239.0.0.10 on port 30001 and the central server will pick it up.
Example:
<?xml version="1.0" encoding="UTF-8"?>
<group>
<name>dsm303</name>
<clock>12:45:21</clock>
<frequency>1</frequency>
<health>Green</health>
<status><![CDATA[<html><h1>MTP Status</h1><hr>Instrument working awesome!<p></html>]]></status>
</group>
Instrument name, something short:
<name>dsm303</name>
Time of status:
<clock>12:45:21</clock>
Expected frequency of this packet in seconds. This is so the receiving software can decide when the instrument is no longer reporting:
<frequency>1</frequency>
A short overall health [ Red or Green, 0 or 1 ? ]:
<health>Green</health>
This section is optional. If it exists it should contain an HTML document which will be rendered on the status web-page available at all computers onboard the aircraft:
<status>
<![CDATA[<html> A status web page </html>]]>
</status>
1.7. SATCOM
Both aircraft are equipped with INMARSAT 3 and Iridium.
- Cost for INMARSAT
- Full time 64Kbps is $10 per minute.
- MPDS (shared 64Kbps) pays by the byte and is about $5.70 per Megabit.
- We have averaged approx $250 per hour, included:
- Chat (IRC).
- 30 parameters to ground every other second.
- Satellite imagery up.
- Small photo JPEG from camera every minute.
- Data Feed to Ground
- A subset of parameters collected on the plane are shipped to the ground.
- Data can be sent every N seconds (configurable on a per project/flight basis).
- File Transfer to/from Aircraft
- Unidata LDM is used to transfer files.
- Delay is typically 60-90 seconds.
- Security, Firewalls, etc.
- The aircraft is firewalled and so is NCAR. Only a few usable ports.
- HTTP, Unidata LDM are currently the only 2 open ports into NCAR.
- Coverage and Dropouts
- Outages of 3-5 minutes are not uncommon.
- In the continental United States, a 10 degree banked turn away from Brazil is enough for the GV to loose contact.
2. Real-time Software Tools & Products
2.1. Ground Database
A subset of the aircraft database is mirrored to the ground.
- Exposed host for aeros database is eol-rt-data.guest.ucar.edu
2.2. Internet Relay Chat (IRC)
Chat is available between participants of a field campaign. Personnel aboard the aircraft can communicate with ground personnel when satellite communications are operational.
Chat server is rdcc.guest.ucar.edu
- You will need a password to connect to this.
- Configuring chat client onboard
- Turn off 'away-tracking', this generates a lot of traffic.
- Problems / issues
- There is no feedback when communications between aircraft and ground go down. Messages disappear into the ether.
2.3. Display Software
Primary real-time display program aeros, both onboard and ground based.
Working on a MapServer product for web based GIS information and aircraft tracking.
2.4. Google Earth
Google Earth KML files are available which track the aircraft. These auto-refresh every 60 seconds. Example KML this file has a specific field campaign coded into it.
3. RAF Post-flight Data
3.1. Data Products
The Primary RAF data product is delivered as a netCDF file. This file includes all scalar and most vector/histogram (PMS-1D) data. Instruments which require large bandwidth to record are typically recorded separately.
3.1.1. netCDF file
3.1.2. PMS-2D
PMS-2D data is recorded in a separate file, follow the 'Description' below for data formats and more.
3.2. Providing Data to RAF for Integration
Data should be provided in netCDF or NcML (an XML version of netCDF).