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  • Writer's pictureDale Hill

Monument Peak NASA Site

Date: August 7, 2021

Distance: 3.30 miles

Total Elapsed Time: 3h 30m

Total Moving Time: 1h 38m

Summit Elevation: 6,249 feet

Elevation Gain: 518 feet

Trailhead: Big Laguna Trail 5E06

Previous Ascents:

  1. July 31, 2021

  2. April 5, 2020


  1. Peakbagger Peaks - 1, Survey Marks - 5

Looking down on the Helipad and NASA Site from Monument Peak

Monument Peak, again...

Last Saturday was my first trail hike since I tore my ACL, it went well enough, but even the short distance and minimal elevation gain of the route to Monument Peak challenged me more than I anticipated it would. Two months of no physical activity took a toll on my fitness level and was a real eye-opener. Generally speaking, my knee held up okay thanks to my new brace, but any descending still had me going REALLY slow. I was most taken aback by the drop in my cardiovascular conditioning, used to dropping people on climbs even with a full pack, I found myself laboring to catch my breath on seemingly simple stretches. Both my strength and cardio condition will return with time, training, and miles logged but reclaiming it is going to take effort.

My objective today was twofold, first I planned to do some trail maintenance on the section of the trail between the Pacific Crest Trail (PCT) and the ridge trail leading up to the communications site at the summit. The second item on my list was to recover/photograph as many of the survey marks related to the NASA site at the summit. I knew there were a couple of survey marks within the fenced-in area that I simply wouldn't have access to, but there was a Permanent GPS Geodetic Array (PGGA) station that I forgot to take pictures of last week, that I specifically wanted to document.

While doing some preparatory research for today's trip, I came across two fascinating site reports, one by the National Geodetic Survey (NGS) and one by a cross-functional team that included representatives from NASA's Goddard Space Flight Center, scientists from ITT Corporation, Honeywell Technology Solutions Inc., and MIT. I'll make reference to those two reports throughout this article, but the short version is that I learned there was a LOT more cool stuff on Monument Peak than the one survey mark I recovered last Saturday!

Getting There, Clipping and Clearing the Path

When I was out here last weekend, the section of trail that branches off from the PCT and heads up toward the summit was thick with manzanita, if I hadn't had my GPS track from last year's hike, I probably would have just blown right by the turn-off because it just looked like a wall of brush. I really wasn't in the mood to stop and clip back the brush last week, but I had resolved to work on it today.

I reached the trail junction and turnoff from the PCT at just under a mile into my hike. The well-worn PCT continued north, while my route headed northeast into the brush. I spent an hour slowly working my way through the first 250 yards of trail, trimming back the brush that almost completely blocked the trail in some places. I had my small pruners with me but probably would have made quicker progress if I'd brought my loppers instead. 🤷🏻‍♂️ Still, it was peaceful and I just plugged away at it. I had mentally allowed myself an hour before I moved on to the rest of my day, as it turned out my stopping point was only about 70 yards short of where the trail met up with the ridge trail that traversed between a small peak to the northwest and Monument Peak. There was more to be done, but even with my climbing gloves on, I was developing blisters from the work. The upside to getting this done was that my return trip was much quicker and easier! 😉

The Helipad

After I recovered the Monument Eccentric survey mark last weekend, I looked out to the southeast and thought it'd be cool to check out the old helipad. I took this photo as I approached and noticed on the opposite side of the pad there was a concrete pillar (point A). Thinking that it may be some kind of survey mark, I headed directly across the pad to check it out. When I got there, it was pretty basic except for the bolt mounted on the top, I didn't even think to take a picture of it at the time. I walked back across the pad, around the fenced-in complex, and headed back down the trail (yes, even forgetting to get pictures of the seismic monitoring unit that I knew was a registered survey mark) 🙄

My first visit to the Helipad on July 31, 2021

SLR Calibration Piers

It wasn't until I got home and found the Monument Peak Site Baseline Report, Prepared for the Goddard Space Flight Center Space Geodesy Project that I understood the significance of that plain concrete pillar. The pillar was one of two Calibration Piers for the MOBile LASer System (MOBLAS-4) set up on Monument Peak. Today I buzzed around and took lots of pictures of all the various control points at the summit (to the extent possible without access to the compound). The first two images below are of Calibration Pier C.

I've also included pictures of Calibration Pier A, this one is just off the road due south of the summit. Most people who hike to Monument Peak know this one because it has a "DANGER Laser Target" sign facing the road. The orange unit mounted on the top of Cal Pier A is a corner cube used by the Satellite Laser Ranging (SLR) System. In laymen's terms, it reflects light back the way it came, regardless of the direction, it's a type of retroreflector, I found a NASA PowerPoint presentation called An Introduction to Retroreflectors and Arrays, but my head started to spin with all the science 😵‍💫 (there are reasons I chose the Accounting profession over Science!) 😂


The other resource that I found was a Foundation CORS Program Site Survey Report of Monument Peak that was prepared by the National Geodetic Survey (NGS). One of the great things about this report is that it documents all of the various control points at the site and includes pictures with a brief description of each point. I couldn't believe that I had walked across the helipad last weekend and didn't realize there was a survey mark there! Had I walked around the perimeter of the pad, I most definitely would have seen the brass disc set in the apron of the helipad. LOOKOUT does not have an assigned PID in the NGS database, but it is described in the report as:

A NASA BFEC survey disk set in the west side of a round concrete pad used for helicopter landings. Stamped LOOKOUT 1988. The datum point is the bottom of cast dimple near the center of the disk.

The Calibration Piers and the LOOKOUT survey mark are all considered Ground Network Marks. Ground marks are monumented for future reference and are considered passive marks (they are targets to bounce signals off of as opposed to emitting signals themselves) A terrestrial survey ties them together in a local coordinate system using high-precision horizontal/zenith angles and distance measurements.

Leaving the helipad, I headed over to the fenced-in compound to photograph what I could through the fence.


For the uninitiated, non-technical, or non-"sciency" people, it can get confusing trying to sort out what equipment is what. Even with the site reports I mentioned above, I found that the station MONP (Monument Peak) CORS (Continuously Operating Reference Stations) Point actually has two different Permanent Identifying numbers (PIDs) assigned by the National Geodetic Survey: AB5054 and AF9705, probably just a case of the NGS not catching the duplicate and deleting it from the database. 🤷🏻‍♂️       

The CORS Point is the dome that houses an IGS tracking unit on a deep-drilled braced monument. Sidebar: I served a career in the US Air Force and though the military had cornered the market on Acronyms within Acronyms, however, they don't have anything on the scientific community! IGS stands for the International GNSS System, GNSS, in turn, is short for the Global National Satellite System. This station is one of many in the Permanent GPS Geodetic Array (PGGA) a network of permanent monitoring GPS stations in southern California devoted to the continuous measurement of crustal deformation in near-real-time, phew, that's a mouthful. The PGGA which began as a NASA pilot project with four active stations in 1990 is operated by the Scripps Institution of Oceanography in collaboration with JPL, MIT, UCLA, Caltech, USGS, various Califomia county surveying offices, Caltrans, and the Southern California Earthquake Center. I had previously found one of these units on Mount Harwood when I hiked Mount Baldy last year. The EarthScope station SCS1 is to the right of the MONP. Each station is self-contained, using solar panels to recharge the batteries that provide power to the seismometer and other sensors and electronic systems. The entire instrument is placed in a vault and buried six feet below the surface. According to the National Science Foundation, these stations are extremely sensitive. They can detect earthquakes at magnitude 5.0 or greater--"sensing" them as far away as the opposite side of the planet--as well as record smaller quakes that occur regionally and locally. Each station includes a high-performance barometer and an infrasound microphone, and sensors to record temperature and pressure. This configuration may also be referred to as a Plate Boundary Observatory.

You can learn more about the EarthScope Stations on their archived website. There is also a new joint program called the EarthScope Consortium that can be found here. The new joint entity is still in its early stages, so it may take some internet sleuthing to find the data you want, but it should be there.


This station appears very similar to the Calibration Piers, it's a simple concrete column with a brass screw set in the center and 3 other pins that were used to mount the DORIS Antenna set atop the column. There is a photograph in the Site Survey report that shows a small forced centering device set up over the MOOB Mark and one of the reports had old photos of the antenna on the pillar, but as noted in the site survey, the antenna has since been decommissioned. While I have been unable to find a definition for "MOOB" it is clearly the reference point used to calibrate the exact position of the antenna.

MOOB MARK. A domed brass screw near the center of the DORIS concrete pillar. No stamping. The datum point is the bottom of a punch mark in the top center of the screw. The DORIS antenna has been decommissioned and removed.

DORIS, short for Doppler Orbitography and Radiopositioning Integrated by Satellite, is a French satellite system that emits a signal that is picked up by a receiving satellite which is basically the opposite of how the GPS system works (the satellite sends the signal to ground-based receivers). According to the linked Wikipedia reference, there are about 50-60 ground stations that make up this system. Truly, the underlying science is well beyond me, and I am by no means an authority on this, but this is a fun educational endeavor learning about all this stuff. It never ceases to amaze me what educational rabbit holes my survey mark hunting will take me down!

The Remaining Survey Marks

There are still four survey marks that I have yet to recover, they are all located inside the fence and require coordination with the Bendix Field Engineering Corporation employees who manage the site. There are two National Geodetic Survey brass discs: MONUMENT PEAK NCMN 7274 (PID: DC1438) and its reference mark: MONUMENT PEAK NCMN RM NO. 1 1983 (PID: N/A) There is also a metal plate in a square concrete post that is stamped ARIES ORION STA 7220, (PID: DC2123). The final station, A NASA-GSFC survey disk set in a concrete post, stamped ORT STATION 7110 1981 (PID: N/A). Of the four remaining marks, I was able to get initial photos shooting through the fence for two of the marks NCMN 7274 and the Aries Orion Station, both marks are covered by small trash cans (I'm not sure why since they are within the boundary of the fenced-in site, but who knows?) Between the maps provided in the previously referenced reports, and verifying my photos with the photos associated with the NGS datasheets, I consider these "pseudo-recoveries"😉, I will have to make arrangements to access the site and document these "up close and personal", but for now, this is the best I have. 🤷🏻‍♂️  


It definitely felt good to get back out this week and hike this trail again, it's a slow process coming back from this injury so every little bit helps. When I originally hiked this in 2020, I wasn't able to find the survey marker at the summit (despite performing what I thought was a thorough search). When I went back last week, I knew what I was looking for at the summit, and was successful in recovering the mark, but totally forgot to take pictures of the CORS Point (my primary objective for today). When I searched for information about the discs that were inside the fence, I sort of hit the "Science Goldmine" that led me down a rabbit hole that was way too technical for me 😳 but interesting nonetheless. So I will return for a final visit when I can schedule an appointment to meet with the site crew, I also hope to learn a little bit more (in laymen's terms) about what their current role and mission are. I am constantly amazed at what I have discovered and learned through this new hobby of searching for Survey Marks. Of course, it'd be easy to just photograph, document, and log the marks in my database, but every mark has a story. It could be about the mark itself, what it identifies, the region, people, and cultures surrounding where it was set. The hunt is only half of the fun, the educational component is the other half.‍ 🧠

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