Ancillary (Weather) Calibration Devices

TIP Last Update: JeffMangum - 11 February 2014


Ancillary Calibration Device Memos (ALMA, EVLA, etc.)

Chajnantor Weather Station Access Points

Atmospheric Models

Weather Station Delivery Status

  • Eight sets of computers plus weather monitoring equipment (see the weather station instrumentation description for details) were purchased by ESO (Leonardo Testi) around 2008/07/03.
  • Equipment arrived and was successfully imported into Chile on 2008/07/25.
  • See planned station locations description below.
  • Seven sets of instruments (save one for spare) will be located within the 10 proposed AOS locations listed below.

-- JeffMangum - 26 Aug 2008

Weather Station Installation Planning

  • First set of production weather station instruments installed at the OSF, on holography tower #2, in late 2008.
  • See AIVMAN-1645 for further information on the verfication of this OSF weather station.
  • On 2009/04/29 Richard Hills and JeffMangum decided that it was best to continue with verification of these weather station systems at the AOS.
  • Joe McMullin and Eduardo Donoso were contacted in late-April 2009 regarding the implementation schedule for the installation of this first weather station location at the AOS (the "array center" location near pad A71; see below).
  • Based on limitations associated with infrastructure (power and ethernet) installation on site, the plan for installation of the first AOS weather station is as follows:
    • Temporarily install METEO1 near the AOS technical building by 2009/09/01.
    • Move METEO1 to its permanent home in the weather station shelter building (the old site characterization containers) on 2009/12/01.
    • Install METEO2 with METEO1 to perform cross-calibration checks of the sensors.
  • 2009/12/09 Update: Richard notes that...
    • First weather station will be installed near the ACA, or array center, by 2010/12/30.
    • Remaining six weather stations are to be installed by 2011/10/01.
    • In practice we would very much like to have two or three additional stations in the Inner Array area by say Jan 2011, so we have that information as we start to build outwards. Eduardo Donoso notes that this will be coupled to fiber and power installation on the site.
    • We need to clarify exactly where the first weather station will be installed. Is it close to the position identified for the Central Weather Station (see figure 1 of the attached ICD)? We have been assuming that this is what is planned, but would like this assumption confirmed.
    • Note that we expect to have the temperature profiler, which goes in the Central Weather station by second quarter of 2010 so we need to have the infrastructure to support that by then as well.

-- JeffMangum - 2009-12-09

Discussion Regarding Power and Ethernet Requirements for Weather Stations

On 2008/09/08 Eduardo Donoso commented:
Hi Jeff:

The document seems to be Ok, I still have some doubts as how an Ethernet 
connection may happen, as we are going to install fibers from the AOS TB 
to the antenna pads. How does an Ethernet cable appear from there, I do not know.

The power may come from a transformer and switchgear near the meteo post.

The installation of these facilities is unknown, as there has been a great 
delay in the foundation construction. The PMCS group is working on the new 
utilities construction at the AOS.



Site (Donoso) and Computing (Glendenning) had been informed about power and ethernet requirements from the beginning of design development (~2004), so it is not clear why there is a problem with this now.

Following up on this discussion, Leonardo Testi consulted with Gianni Raffi and commented on 2008/09/09 that:
He says that the computing fibers at the Antenna pad will be active only 
when an antenna is actually sitting on that pad. Deploying the weather 
station with a local computer imply that we need to bring the network 
to the meteo tower separately from the antenna pads network (if I got it right).

He was not aware of our plans to have local computers, but had assumed 
that we would control the equipment from computer(s) stored in the AOS 
tech building, in a controlled climate condition. I am not sure this is 
an option that we have at this point, and in any case we still need to 
think how we connect the weather instruments to the computer, I would 
think that the AOS building is a bit too far for a serial cable.

As mentioned above, Computing was informed of design needs for power and ethernet.

AlWootten believes that the limitations are:
  • Ethernet: Limited switch capacity. Likely solution is to install a switch with more ports.
  • Power: Not clear what problem is, but alternative solution is to provide power with solar cell.

AlWootten will bring this issue up at IPT meeting on 2008/09/15

-- JeffMangum - 14 Sep 2008

Resolution Following 2008/09/15 IPT Telecon

AlWootten notes that, as a result of the IPT telecon discussion of 2008/09/15:

  • Shelter: AlWootten responded to Eduardo's comment, to which he had already responded in the revised document. Site did not provide for the shelter (although this was placed into the ICD by Eduardo's predecessor). AlWootten proposed reusing the container, which was originally a proposal from Eduardo's predecessor and seems a minimal money investment.
  • Fiber: Eduardo noted that the fiber was procured. Fabio noted that the report of the June site infrastructure review was out and that there were mistakes noted in addition to non-optimal solutions to the fiber layout. In his opinion, the plan would need to be readdressed in any event and the inclusion of additional fibers for the weather stations was a small problem. Eduardo noted that there would be some details in the connection at the antenna pads.
  • Power: The power distribution is three phase 440 V. Donoso noted that two phases provide the necessary voltages to run the weather stations. Making sure that this is done at the site is a matter of field engineering, a locally solved problem.

-- JeffMangum - 18 Sep 2008

Weather Station Instrumentation

In the following I list the proposed weather (P, T, RH, WS, WD) instrumentation to be purchased for the ALMA site.

Pressure, Temperature, and Relative Humidity Sensor

In considering the hardware options resulting from our vendor investigation, I realized that it might be better to use a slightly less capable, more reliable humidity and temperature sensor and buy more of them with the goal of getting a better site-wide distribution of this important quantity. We can still supplement the equipment from this purchase with our existing chilled-mirror hygrometer systems.

  • Sensor: Vaisala PTU303. This model of the 300 series is for outdoor use. Will mount with the HMT330MIK installation kit. Costs about $2500 per unit.


-- JeffMangum - 20 Feb 2007

Wind Speed and Direction

  • Sensor: Vaisala WMT50. Seems to meet all of our specifications. Costs about $1000 per unit. Note that this unit only measures wind direction and not the vector wind (like the Metek sonic anemometer at the ATF site). The cost is about 10 times higher for vector wind measurement devices.


-- JeffMangum - 20 Feb 2007

Note that BryanButler informs me that the EVLA will install WXT520 devices for their weather stations.

-- JeffMangum - 2010-04-14

Weather Station Locations

JeffMangum suggests the following for the ALMA weather station locations. Antenna pad locations are listed for now, with the exact location for each weather station sited near these antenna pad locations based on:

  1. Relative location requirements detailed in the weather station instrumentation specification, and
  2. Site IPT recommendations (i.e. access to utilities, proximity to roads, etc.)

I have used "configs_11Apr07.xls" spreadsheet of antenna pad locations for reference. Note that all other "ancillary" calibration devices (tipper, O2 radiometer, phase monitor, etc.) should also be sited near the array center weather tower (antenna pad location number 83).

ALMA Weather Station Locations

Chosen such that:

(1) <= 100m of elevation change between stations along each arm.

(2) Sufficient sampling along each arm to allow interpolation of
    (P,T,RH,Ws,Wdir) measurements.

Pad Name       Pad ID        UTM-x           UTM-y             Note
--------       ------      ---------       ----------  ----------------------
West Arm
W201         Y50         620125.00       7453657.00
W205         Y46         623451.00       7455040.00
W208         Y42         625901.90       7457210.20
A130           142         626124.00       7452986.00

South Arm
S309         Y39         634062.00       7447310.00
S307         Y32         632668.20       7451111.20
S301         Y29         629490.20       7450388.20

Pampa la Bola Arm
P413          Y28         633309.90       7462869.20
P410          Y24         631556.80       7458399.50
A129           141         628978.00       7454297.00

Array Center
A71             83         627706.03       7453210.35    Corresponds
                                                         to "Option A"
                                                         of BVV
                                                         central array
OSF            ...         ...             ...

-- JeffMangum - 15 Aug 2007

On 2007/10/24 Eduardo Donoso confirmed that our proposed weather station locations are compatible with power system availability on the site. Eduardo said: We reviewed your proposed locations for the meteo stations on the high site to see if there are power sources nearby. We found the locations that have a transformer nearby to feed the station and the results are showed below. Note that all proposed stations have a transformer nearby, so we have no change to suggest. We keep the suggested locations then.

-- JeffMangum - 24 Oct 2007

AOS and OSF Pad Naming Convention

Weather Station Naming Convention

Discussed weather station naming convention with AlWootten and RalphMarson (at Ralph's request...he is working on software for weather stations). Decided that a name which included the pad name was most appropriate, allowing for easy identification relative to a fixed location on the site. Weather station naming convention will be:

WS+(pad name)

For example, the weather station near pad A129 will be called WSA129.

-- JeffMangum - 2009-03-19

Production Weather Station Data Output Format (Proposed)

Proposed weather station output format is as follows:

UT date and time, wind speed, wind direction, pressure, temperature, dew point, relative humidity, radiation
                ,  (m/s)    ,     (deg)     ,  (hPa)  ,    (C)     ,    (C)   ,  (%),     (???)

The text file is similar to:
2008-10-01T05:11:53.045, 3.51, 195.1, 723.15, 10.41, 2.30, 1.21, 30.011
2008-10-01T05:11:58.032, 3.62, 198.6, 723.35, 10.31, 2.00, 1.20, 30.111
2008-10-01T05:12:03.152, 3.62, 198.6, 723.35, 10.31, 2.00, 1.23, 30.111

-- JeffMangum - 08 Nov 2008

Proposed Conversion of Production Weather Station From SBC to Terminal Server

Tzu Shen proposed to replace the SBCs to which all weather station instruments connect with a terminal server which will transport the serial measurements from each weather station to fiber which will connect to a central computer at the AOS. Specifically, what Tzu wants to do is to:
  1. Convert all R232/R422 signals to TCP packages and
  2. Transport them through fiber optic/ethernet cables and then
  3. Convert them back inside of the Computer Room at the AOS with a more powerful server suitable to handle 7 or 8 weather
  1. In that server we will run the software to read the sensors values and ingest them to the database.

A possible terminal server to do this job is the NPort® 6250 Series.

-- JeffMangum - 2009-06-24

Production Weather Station Installation Tips

Running ReadWS Script in the Background

  • To start the process and have it run even if you log out: nohut ReadWS &
  • To kill the process: ps -aux | grep ReadWS
  • Once you have found the PID use: kill -9

-- JeffMangum - 07 Nov 2008

Ancillary Calibration Instruments Specifications and Requirements Document

The final version of this document is complete. It has also been placed on ALMAEDM under DOCUMENTATION - Science, "Site Characterization" folder, as entry number 5 Ancillary Calibration Instruments Specifications and Requirements SCID- This document:

  1. Outlines the requirements for the instruments needed to provide the atmospheric information necessary for effective scheduling and accurate calibration of ALMA.
  2. Contains a general discussion of the problem and a list of the instruments expected to be most valuable, together with an indication of their roles.
  3. Provides a set of requirements for the measurement of the necessary meteorological quantities (temperature, humidity, etc.) and defines both the output from the instruments and the input to the calibration software.

-- JeffMangum - 11 Aug 2005

Ancillary Calibration Instrument: Database Interface Properties

On 2007/08/24 BrianGlendenning picked-up the topic of how the detailed interface between the ancillary calibration instrumentation and the monitor and control database will be defined. Specifically, what will be the values, units, and default dump rates for each device. This smells like a wiki topic to me. The table below summarizes the definitions. Items in red are planned to be available with the first ancillary calibration measurement systems:

Instrument Measured Parameter Units Range Default Dump Rate (sec) Device CommentsSorted ascending
Pressure Sensor
Atmospheric Pressure (P)
50-1100 mbar
Vaisala PTU300
Temperature Sensor
Atmospheric Temerature (T)
-40-+80 C
Vaisala PTU300
Atmospheric Relative Humidity (RH)
0-100 percent
Vaisala PTU300
Wind Speed (Ws)
0-60 m/s
Vaisala WMT50
Basic windbird
Wind Direction (Wdir)
0-360 deg
Vaisala WMT50
Basic windbird
Atmospheric Flux Versus Frequency
0-300 K
Broadband atmospheric emission monitor. 1000 spectral channels?
Ozone Monitor
0-300 K
High-resolution FTS. Few hundred channels maximum?
Tipping Radiometer
Atmospheric Opacity
Measurements of either voltage/power (uncalibrated) or temperature (calibrated) as a function of elevation will be delivered to TelCal(?) for analysis. TelCal(?)-derived opacity would then be dumped to database.
Water Vapour Radiometers
Atmospheric Water Vapour Content
0-300 K
Probably will be treated separately from ancillary devices. The main quantity output by the production WVRs will be four calibrated double-sideband brightness temperatures. They will likely be read out at 1 Hz in most circumstances. The path of these data within the overall system will be somewhat different from the ancillary instruments in part because they will also be fed directly into the correlator to support the on-line phase correction scheme.
Temperature Profiler
Channel Temperatures as functions of tip angle
0-300 K
Raw 60 GHz oxygen emission spectrum for use with our algorithms.
Atmospheric Phase Monitor
Atmospheric Phase
0-360 degrees
Raw data values (not sure how much processing will be done on them before they are sent out from the APM "system" - so it will either be the complex voltages at each of the antennas, or it might be the relative phase between the antennas) will be produced by the instrument. Then TelCal should probably compute the proper fit values for the structure function (whether the detrending and phase unwrapping is done before or within TelCal is another decision to be taken). The raw phases will be produced of order 1 per second (literally one per second in the current system); the structure function values on timescales of minutes (every 10 minutes in the current system).
Sonic Anemometer
Wind Vector (X,Y,Z)
0-60 m/s
Metek USA1
Sonic anemometer measurements. Assumes existing Metek sonic anemometer will be installed.
Temperature Profiler
Atmospheric Temperature Profile (around 30 data points)
0-300 K
The profile derived by algorithms internal to the device from the 60 GHz oxygen emission spectrum.
Cloud Monitor
Cloud Cover
There are two options for output from this instrument: 1 - archive the actual CCD images (overkill?); 2 - Have some software between the device and the M&C system that calculates, given the CCD frame, the percent cloud coverage, and archive only that (more sensible).

Questions and Issues:
  • Do we really want the wind vector from the sonic anemometer, or would it be better to write the wind speed and direction (at a high rate) from this device?
  • What is the FTS output?
  • What is the WVR output?
  • Is the cloud monitor output just pictures? If so, it probably does not belong in the database (or does it?).
  • Note about the Temperature Profiler: We will very likely want to record both the retrieved temperature profile generated by the device (I guess about 30-50 datapoints) and the raw outputs of the radiometers channels. This is because using the retrieved temperature profile is unlikely to be optimal when using in combination with WVRs to do phase correction -- BojanNikolic.

-- JeffMangum - 24 Aug 2007

Weather Station and Temperature Profiler Technical Descriptions

Two documents have been developed which are designed to describe the weather station and temperature profiler instrumentation for potential bidders. Bid documentation for the ALMA Weather Instrumentation was sent to Purchasing (Bill Porter) on 2006/12/01. Still investigating potential suppliers for the temperature profiler.

-- JeffMangum - 01 Dec 2006

Temperature Profiler

Case for Temperature Profiler

Here is an extract from the ancillary devices document making the case for an oxygen line sounder to measure the temperature profile. More details about the basis for the accuracies quoted can be found in ALMA memo 496.

-- AlisonStirling - 11 Nov 2004

Oxygen Sounder Measurement Details

We have done some further research on the oxygen sounders. There appear to be two main approaches that are used to invert the set of brightness temperatures that the sounder measures to temperature-height profiles:

1) A neural network inversion approach that uses a large database of temperature profiles from radiosonde launches at the site. This approach appears to be in the widest use.

2) A maximum likelihood method that relies on meso-scale meteorological forecast data, and then uses the radiometer data to essentially make a small adjustment to the forecast model.

I would therefore like to know about:
  • Feasibility/cost of a significant number (1000 or more) radiosonde launches at the ALMA site
  • Is ALMA already purchasing meteorological forecasting for the site? What data products?

All of the above is assuming that actually want to know the temperature profile. For the WVR we are only really interested in the conversion factors between 183 GHz measurements and paths, so when using inference techniques it may be simply possible to use the outputs of the O2 sounder as inputs to the inference process and avoid making un-informed guesses about the profile. But others may have other uses for temperature profile data. So another question is :

Is the oxygen sounder data going to be used by any subsystem other then WVR-based atmospheric phase correction?

In terms of timescales, if we are going to be launching radiosondes, then clearly it would be much preferable to have the O2 sounder at the site when these launches are being made.

Finally, given uncertainty in the way the data are going to be used, I would suggest that our procurement specifications concentrated on the accuracy of the brightness temperature measurement by the sounder, i.e., noise temperatures, bandwidths, absolute stability etc. This would be in preference I think to relying on quoted accuracies of temperature retrievals.

BojanNikolic - 11 Oct 2007

The requirement that the sounder needs ~1000 radiosonde launches will require some additional effort. Another option is to get an accurate site atmospheric model. Lars is working with one of the Chilean university groups to work on this modeling problem.

Oxygen Sounder AOS Integration Details

On 2010-12-10 BojanNikolic notes that the temperature profiler is operating continuously at the AOS. We talked briefly at our 2010-12-09 telecon about how to exploit the measurements from the profiler. As requested here is a brief summary:

There are three main areas where these data should be useful:

  1. Absolute calibration: Using the temperature profile should allow better conversion of observed atmospheric emissivity into an estimate of atmospheric transparency.
  2. Phase calibration/correction: There is a temperature dependence in both in the conversion of observed atmospheric brightness into a water vapour content and the conversion of water vapour column into excess path. Constraints on the temperature from the profiler should therefore increase the accuracy of these conversions.
  3. Scheduling: The attached infra-red sensors gives a measurement of cloud cover above the profiler. The retrieved atmospheric profile may also give useful information about overall atmospheric conditions such stability?

Making the best use of the atmospheric profiler in all three of these areas will I think require some further research.

However, it is clear (I think) that the first step should be to ensure that the data from the profiler are archived and attached to relevant scientific data:

  1. Retrieved profiles should be archived (say at a rate of once every three minutes) to an/the ALMA archive, regardless of whether scientific observations are being made or not.
  2. When scientific observations are being recorded, the relevant atmospheric profiles should be attached to the data and propagated into the measurement set for off-line calibration.
  3. The measured atmospheric profiles should also be published for use by the online systems, in particular the TelCAL sub-system
  4. The IR cloud cover estimate and temperature profile should be plotted on a screen in the control room so that staff can make use of this information for scheduling.

-- BojanNikolic - 2010-12-10

BryanButler and RobertLucas commented that there is currently no place in the SDM for this information, but that since the profiles are processed by the profiler itself:

  • We have planned to include these profiles in the ASDM Weather table as new optional columns, as well as the cloud detector estimate. This should be included in ASDMv1.1 coming with ALMA-R8.1 (release Jun 2011). Actual filling of these columns might come later. RobertLucas knows of no plans to include this in the MS.
  • Once the columns are added to the ASDM weather table it will be possible to publish the measured atmospheric profiles for use by the online systems, including the TelCal subsystem.

-- RobertLucas - 2010-12-15

ATM Evolution

Juan Pardo comments that the evolution of the ATM C++ interface and its retrieval methods can be tracked at: Please send Juan any inquires regarding this implementation and the Ancillary Devices possible needs.

-- JeffMangum - 27 May 2005

BojanNikolic has posted a downloadable version of ATM at This version is maintained under CVS and GPL licensed.

-- JeffMangum - 2009-01-20

Action Items

Assigned to Due date Description State Notify  
JohnRicher 2005-05-15 Ancillary measurement devices specs and reqs document. (go to action) closed JohnRicher, AlWootten, JeffMangum edit
AlWootten 2005-06-01 Science/Site ICD for Ancillary measurement devices submitted. (go to action) closed AlWootten, JeffMangum edit

Assigned to Due date Description State Notify  
JohnRicher, AlWootten, JeffMangum 2005-09-01 Ensure the TelCal software plan is consistent with the proposed ancillary measurement device instrumentation suite. (go to action) closed JohnRicher, AlWootten, JeffMangum edit
JeffMangum 2006-07-01 Begin procurement of Ancillary Devices. See Ancillary Devices Specifications and Requirements document for details. (go to action) closed JeffMangum edit
JeffMangum 2008-10-01 First ancillary instrumentation set installed at OSF. (go to action) closed JeffMangum edit
-- JeffMangum - 11 Aug 2005
Topic revision: r64 - 2014-02-11, JeffMangum
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