First Weather Station on the Surface of Mars

Of course we’ve all heard and seen the fantastic news of NASA’s Phoenix lander making a successful three point landing on the red planet. The primary goal of the Mars Phoenix Mission is to detect life or the traces of it. However a secondary goal is to measure the weather at the surface continuously over a long period of time.

Today in a group of raw images returned from the lander is the first photo of the weather station mast after deployment. I’m pleased to present it here:

On further inspection though I note that there appears to be something dangling from the top portion of the sensor apparatus, see the arrow:

I don’t know if this is normal or if something has come loose and what we see is something dangling on the end of a wire. Given that this mission was put together on a low budget, using parts previously designed for other spacecraft, it makes me wonder if the weather station we see above isn’t simply this low tech device.

Here is a pictorial view of the lander and the position of the MET mast:

Click for a larger sized image

Here is a description of the MET station from Wikipedia:

The Meteorological Station (MET) will record the daily weather during the course of the Phoenix mission. It is equipped with a wind indicator and pressure and temperature sensors to do so. It is also equipped with lidar (laser imaging detection and ranging), which will be used to find the amount of dust particles in the air. It was designed in Canada and supported by the Canadian Space Agency and a team headed by York University The Geological Survey of Canada will oversee the science operations of the station, which was built by Canadarm maker MacDonald Dettwiler and Associates Ltd. of Richmond, B.C.

The lidar laser is a passive Q-switched Nd:YAG laser with the dual wavelengths of 1064 nm and 532 nm. It operates at 100 Hz with a pulse width of 10 ns. The lidar is vertically pointing. The scattered light is received by two detectors and operates in both analog and photon counting modes.

All types of backscattering (for example Rayleigh scattering) are the basic effect used for the lidar. With the delay between the pulse and the light reflected by the particles in the atmosphere the distance is calculated. Additional information can be obtained from backscattered light. The polarization makes it possible to discriminate between ice and dust. The line width is an indicator for the Brownian motion of the particles and therefore an indicator for the temperature.

The lidar will get information about the three-dimensional structure of the planetary boundary layer by investigating the dissipation of dust, ice, fog and clouds in the local atmosphere. The wind velocity and temperatures will be monitored over time and show the evolution of the atmosphere over time. Dust and ice contribution in the atmosphere and the formation of dust devils are in the science focus of the instrument.

Judging from experience in installing many weather stations myself, I’d venture a guess to say that the greatest effect on the long-term reliability of the MET station will be the dust. Very fine dust can penetrate and clog even the most carefully designed systems.

I assume there will be public weather data available at some point, and if so I’ll make it available here.

The parking lot effect: temperature measurement bias of locations

NOTE: David Smith is doing experiments with the portable USB digital thermometers that are available here. This sort of experimentation is easy and inexpensive to do, and makes a great topic for a student science fair project. The results are easy to download from the USB thermometer into a PC for analysis. -Anthony

Seven Days in May

A guest post by David Smith

This is an update on recent field tests with remote thermometers (see the ”Fun with Thermometers” post for  background).

My goal is to quantify, to an extent, the effects of microsite problems (pavement, buildings, trees, etc) on temperature.

In the current test one sensor (”A”) is currently in an abandoned baseball field at least two hundred feet from any paving, tree, structure, etc other than a chain-link fence:

This reasonably approximates a good-quality site, isolated from human microclimate effects.

The other sensor (”B”) has a split personality. On one side is a poorly-drained field while on the other side is an older asphalt parking lot:

When the wind blows from the north this second sensor tends to reflect the characteristics of the soggy field, while a southerly wind brings air from the parking lot.

An aerial view of the two sites (”A” and “B”) is here:

 

For this update I selected seven days in May in which the skies were mostly clear throughout the day and night. This should maximize any radiative effects on temperature. (Unfortunately, the site is warm, quite humid and windy this time of year, limiting the magnitude of any radiational microsite effects. But, despite this diminished magnitude there are still useful observations to be made.)

Below is a plot of the average temperature of “B” on five clear-sky days when the breeze was from the parking lot and the average of two clear-sky days when the breeze was from the soggy field. I’ve subtracted the temperature of the nearby baseball field (”A”) from these two averages so that the lines show how much warmer or cooler “B” is than “A”. I’ve also slightly smoothed the data.

All seven days were breezy, which mixes air and limits its time over the surfaces, so the effects are probably muted compared to days with less-breezy conditions:

 

This shows several things. One, when the wind is from the parking lot (red line), the temperature at “B” sensor is warmer than that of the baseball field, night and day. Shortly after sunrise the difference diminishes, presumably due to the higher heat capacity and thus slower warming of the asphalt vs the baseball field. As the sunny day progresses the heat content and temperature of the asphalt rises, reaching a relative peak at “B” in the late afternoon. As the sun sets and evening progresses the temperature of “B” remains elevated but to a smaller extent.

This “parking lot effect” should be noticeably greater this summer, when average windspeed and air mixing diminishes.

 The effects when the wind is from the soggy field (blue line) are perhaps even more interesting. The temperature of “B” tends to be depressed vs the baseball field during daylight hours, presumably due to evaporative cooling of the soggy field. The effect is reversed a bit in the late afternoon, possibly when the dry baseball field is radiatively cooling faster than the soggy field.

The soggy field appears to be due to changes in drainage following a yearlong construction project nearby. This change in drainage and probably ground cover was subtle in nature and may have stretched over some time, something which may or may not be detected by a discontinuity algorithm. In this instance it was cooling but my conjecture is that most drainage changes are towards drying, and warming, not wetting and cooling.

These seven days in May are affirmations that it is a bad idea to have sensors in the vicinity of human-induced microsite changes. Changing drainage, repaving the parking lot, aging of the parking lot, changes in parking patterns, etc can all have an effect. The size of the effects in a given year may depend on rainfall, wind anomalies, etc, making it difficult to detect a discontinuity. 

More to come.