Travel to Chajnantor — APEX and ALMA
APEX Chajnantor Site
ALMA (the Atacama Large Millimeter/submillimeter Array) is the major new facility for observations in the millimetre/submillimetre regime. ALMA is comprised of a giant array of 54 12-m and 12 7-m antennas. ALMA is at one of the highest observatory sites on Earth, at an elevation of 5,000 metres on the Chilean Chajnantor plateau. The ALMA project is a partnership between Europe, Japan and North America in cooperation with the Republic of Chile.
The Chajnantor plateau is also the site of APEX, the Atacama Pathfinder Experiment, a 12-metre diameter antenna observing the Universe at millimetre and submillimetre wavelengths. APEX is a collaboration between the Max-Planck Institute for Radioastronomy (MPIfR), the Onsala Space Observatory (OSO), and the European Southern Observatory (ESO). The telescope is operated by ESO.
How to reach Chajnantor
If you arrive by own means, the ALMA Operations Support Facility (OSF), at 2900 meters above sea level, is located 40 driving minutes from San Pedro de Atacama. Note that transportation for the public visits is arranged (see here). The drive from the OSF to the Array Operations Site (AOS) and APEX, located at 5000 m altitude, takes about 50 minutes (~25 km). At the AOS are the antennas and the Correlator. Only ALMA certified vehicles and drives with an ALMA “driver’s license” are allowed to get to the AOS. Children under 16 years are not allowed to go up.
Arriving by plane
Please note that airfares to and from Chile can get quite pricey when booking shorter than 3 months in advance. The closest airport to Chajnantor is the El Loa International Airport located in Calama, about 120 kilometres west of the observatory. There is no public transport to Chajnantor, so you will need to rent a car.
Arriving by car
There are several car rental companies available at the airport, including Alamo, Budget, Econorent or Hertz. The average daily cost of a car in Calama rises to CLP 65 000 (about EUR 100) and it takes about two and a half hours to drive to OSF from the airport. Very important: Please note that you must request a car without "GPS safety system", otherwise the engine will be automatically blocked as you approach the border to Bolivia on the way up to Chajnantor. Also please note that, for authorized visitors to the ALMA site, a 4WD pick-up vehicle (called "truck") with anti roll bar inside the cabin is compulsory.
To drive from a different city, take the Panamerican Highway as far as the turn for route 25 to Calama. Pass the El Loa Airport, and take route 23 to San Pedro de Atacama. After San Pedro take the route to Toconao until you reach the ALMA/APEX main gate (before Toconao). It takes about four hours to reach APEX from the Panamerican Highway. Please be aware that the road from the ALMA/APEX main gate is private. Only authorised visits are allowed to enter.
Facilities at Chajnantor
The ALMA Operations Support Facility (OSF) is the base camp for the every-day, routine operation of the observatory. It is located at an altitude of about 2900 meters, quite high compared to standard living conditions, but still quite acceptable for scientific projects in astronomy of similar scope. At the OSF are the camp, cantina, antennas assembly sites, labs, control room, etc.
The APEX Sequitor Base, located nearby San Pedro de Atacama in Chile, is the workplace of the astronomers and support staff running APEX, the Atacama Pathfinder Experiment. Sequitor Base is also an administrative point that supports the operation of the antenna and serves as connection between APEX and the rest of the ESO sites in Chile. It is also an important contact point for the local authorities and the people of the Sequitor community.
Accommodation and Food
Only astronomers, engineers and support staff have access to accommodation and food on site. Media visits are allowed on special request. For further information on media visits please check here. ESO staff and special visitors usually stay and eat at APEX Sequitor Base, ALMA OSF or at La Casa de Don Tomás in San Pedro de Atacama. Further information on restaurants in San Pedro de Atacama is available here.
Wi-Fi Internet connection is available at the ALMA OSF.
Cell-phone signal is typically good in San Pedro de Atacama and at ALMA OSF. The quality of the signal worsens at ALMA AOS.
Experience ALMA and APEX with ESO's Virtual Tours.
Health & Safety
Weather and Clothing
At the OSF the days are generally warm, but the nights can be cold. At the AOS, at 5,000 m, it can be very cold with strong winds and one needs a ski parka or a down jacket, gloves, a hat with ear protection, and wind trousers. Sun glasses, hats and strong sun blocking cream are needed at the OSF and AOS. Here you can find climatic information about Calama and San Pedro de Atacama. Also find the current weather forecast for San Pedro de Atacama here.
High Altitude Health Issues
There are inherent risks in traveling at high altitude. The information below is designed for general information, and is not a substitute for specific training or experience and does not constitute medical advice. If you have any questions or concerns please consult to your doctor.
When visiting the APEX/ALMA observatory site, you should be prepared to recognize and respond to the symptoms of altitude illness caused by the lower level of oxygen available at high elevations. The human body can adjust to changes in altitude, by the process called acclimatization.
If you are interested in reading more:
- Although it is no guarantee against problems at high altitude, having a generally good fitness may help you adapt
- Avoid alcohol
- Avoid any unnecessary medication (since their effects may be increased at high altitudes). Sleeping pills, tranquilizers and narcotic-based pain relievers, in particular, can cause serious problems at high altitudes because they can decrease breathing rate. Consult with your health care provider about any medications you plan to bring with you.
- Avoid smoking
- Avoid being very active after you arrive, and get plenty of rest
- Drink plenty of water
Symptoms of Altitude Illness
- Muscle aches
- Loss of appetite
- Nausea or vomiting
- Swelling of the face, hands and feet
Danger signs include severe headache, extreme fatigue or breathlessness (especially while resting), and any neurological problems such as stumbling, confusion, poor judgment or changes in consciousness. It is crucial to descend until symptoms begin to diminish if these signs are present.
Consult your health care provider or travel medicine specialist for specific recommendations about prevention and treatment.
Special Health and Safety advisory
A visit to ALMA or APEX at the AOS at 5000 metres altitude at the Chajnantor Plateau, has some significant safety, security and health constraints. Upon arrival at the OSF, the visitor will be given a safety talk explaining the rules and procedures that have to be duly respected. All AOS visitors are required to:
- Have slept at least one night in San Pedro de Atacama or Calama for acclimatization before they can go up to the AOS.
- Undergo a paramedic medical check-up (blood pressure, blood oxygen level) by the OSF paramedic. Those who do not pass the test will not be allowed to continue to the AOS. As described in the ALMA Safety Manual (14 Feb. 2012) individuals presenting the following characteristics may not ascend:
- Systolic blood pressure level greater than 160 or diastolic pressure greater than 100mm Hg. “Prophylactic” anti-hypertension treatment will not be administered.
- Heart rate greater than 95 beats per minute or lower than 45 beats per minute.
- A blood oxygen saturation level below 70%, or below 80% when showing symptoms of headaches, dyspnoea, tachycardia, blood pressure changes.
- Anyone with a blood pressure level less than that described above, but showing symptomatic indications.
- Any person in the camp or during the check-up who shows signs of altitude sickness (fatigue, dyspnoea, headaches, sleep disruption, tachycardia, palpitations).
- Patients with a history of AMI (acute myocardial infarction), without the authorization of an attending heart specialist. The authorization should expressly state that it is for an altitude level of about 5000 meters.
- Patients with a history of any form of cardiac insufficiency.
- Diabetic patients should be assessed via a hemogluco-test before ascending. Decompensated diabetic patients cannot ascend (a hemogluco test above 200 mg/dl).
- People travelling to the AOS must meet the requirements given in the ALMA Safety Manual (on p. 91-93 in the version of 14 Feb. 2012), which is the authoritative text and must be consulted for full details. In particular:
- External Visitors (defined as any person not in a contractual or working relationship with any of the executives or JAO, e.g. journalists) staying at AOS less than 2 hours: need to sign a waiver form before every visit (the paramedic medical check-up is also repeated if AOS is visited on multiple days). Media visitors or others visiting as part of a job assignment may wish to consult with their supervisor or Human Resources department before signing.
- External Visitors (defined as above) staying at AOS more than 2 hours: a certificate from an occupational physician, stating on the basis of a medical examination (generally referred to as the High Altitude Medical Examination, HAME), that the individual is fit to perform work at 5000 metres, is required (less than one year old). The relevant extract to show to the occupational physician is on page 93 of the ALMA Safety Manual. Media visitors or others visiting as part of a job assignment may wish to consult with their supervisor or Human Resources department.
- All Contractors (defined as any person in a contractual or working relationship with any of the ALMA executives or JAO, including so-called “free-lancers”):
- a statement is required from their Human Resources department which asserts that the person in question is covered by their work accident insurance to work at 5000 metres, or
- a certificate from an occupational physician, stating on the basis of a medical examination (generally referred to as the High Altitude Medical Examination, HAME), that the individual is fit to perform work at 5000 metres, is required and needs to be repeated every year (at least in part). The relevant extract to show to the occupational physician is on page 93 of the ALMA Safety Manual, or
- in the special case of free-lancers without work accident insurance, you may sign a waiver form although it is recommended that you also consult your physician.
- Members of staff of the ALMA executives or JAO: please consult your human resources department for full details, but in particular a certificate from an occupational physician, stating on the basis of a medical examination (generally referred to as the High Altitude Medical Examination, HAME), that the individual is fit to perform work at 5000 metres, is required and needs to be repeated every year (at least in part). The relevant extract to show to the occupational physician is on page 93 of the ALMA Safety Manual.
High Altitude Medical Exam (HAME)
ESO staff or Contractors must follow the rules given in the ALMA Safety Manual (on p. 91-93 in the version of 14 Feb. 2012). The relevant extract is on page 93 of the ALMA Safety Manual. The examination is generally referred to as the High Altitude Medical Exam (HAME), and needs to be repeated every year (at least in part).